Hello all,
(1990 Camaro IROC-Z, 305 TPI, A/T)

Slightly long, but I will explain all (sorry)...

I was looking for some opinions on replacing my fuel injectors. After my vehicle warms up (to operating temp. or after running it rough) it begins to have idle issues. When in drive or park (at a stop, closed throttle) the RPM bounces from 100-500 very sporadically (viewing my dashboard cluster). I can feel the engine doing it while cold, but it is not as noticable (as the RPM won't bounce, idles around 500-700). I wouldn't say that it's a total misfire, but one or some of the cylinders doesn't seem to be combusting properly.

I did have a few idle issues before, however, I cleaned the IAC valve and also adjusted my TPS. I didn't touch the actual minimum air screw though, as it seems everywhere I read they don't give specs. (as it's "factory set") and my idle seems to be fine when cold/on average.

Which leads me to my injectors. I tested the resistance of the connectors and they all read around 2-2.2 ohms (should be 1-2 I believe), so I assume the electrical is fine. However, after testing the actual injectors, there were two (the two farthest to the front, don't know the cyl. #'s off hand, sorry) that read only 9 ohms and another in the back that read 12 ohms. The other 5 were around 16-16.6. From my knowledge they all should read between 16-18 ohms?

I came to the conclusion it may be my injectors causing me my issues and considered replacing them all. (the vehicle has around 140,000 miles)

However, after checking the pricing its nearly $400 to obtain injectors and the gasket set(s).

Therefore, curious if anyone has any other things to suggest trying before spending a bunch of money on something that may not even be the issue.

Sorry for the long read and thank you in advance.

PS - Nearly forgot to mention... I recently (as in 2 weeks ago) did a tune up on the vehicle, including... new plugs, wires, cap, rotor, fuel filter, pcv valve and air filter. Under the distributor cap, I noticed quite a bit of rust but it didn't seem to be the actual cap or rotor that had rust on it, so I eliminated it as an issue? This problem also existed prior to the tune up.

 

That injector reading 9 is definitely bad. I would trashcan them all, replace them with some bosch III.

 

there is a proper way to adjust the min idle screw.

first warm up the engine to operating temp. then unhook the IAC valve.
then adjust the screw until you reach about 500 rpm in gear. (this is according to a haynes manual)

although I can't get mine down to 500 rpm in gear.

then check your TPS reading and adjust it to read .54-.56 ohm


since you seem to have a problem only after warm, I would suspect the coolant temp sensor or fuel pump. ( I had a fuel pump that would stop producing enough psi about the same time the engine came up to temp) that was a real head scratcher. and you know how hard it is to get the tank out of these cars. boy I was dreading replacing it.

 

you need injectors. Go to www.fuelinjectorconnection.com and get a set of Bosch 3's the kit with the gaskets, seals and injectors is under 200 i believe

 

Thank you all for your information, it is greatly appreciated!

It appears that replacing my injectors is in order, after all I do know that 3 of the 8 are bad for sure (2 with 9 ohms and 1 with 12 ohms)... however I never considered the fuel pump or temperature sensor. The idle seems to be fine when the engine is cold and I adjusted my TPS sensor to be dead on when I cleaned the IAC Valve.

I will most likely check my fuel pressure (to ensure the pump is working at optimal) and then replace the injectors. If this doesn't fix it I will check out the temperature sensor.

Regardless, I will most likely complete this over the next few weeks or so and post back my results. If anyone has any other opinions please feel free to enlighten me!

Thanks again

 

are those reading from the injectors when they were hot?
if not, then they are probably worse than you think.
when heated up, the resistance normally goes down.
the old injectors off my car read anywhere from 12~16 ohms cold.
hot some were less than 5 ohms. none were higher than about 14 ohms.

 

Also Should be noted that ohm's only check the coil in the injector. Not that they are properly functioning. So definatly replace them if the ohms are low, Best investment of all time is a good scanner. That way you can auctually see if they are opening not just if the coil is bad. Southbay has a sale for thirdgen member's on Bosch 3's for like 145$, and tou wont need to double O ring they are plug and play. Code is like tg11 for 10% off.

 

You might also want to see if it's the ignition control module on the distributor. My car wouldn't restart after it was warm and that fixed it. It's not the same problem but that seems like it could be a possibility to me.

 

Its the injectors...my car does the same thing. My entire right bank (#2, 4, 6, &8) are below 10, so it runs like crap once its warm. Try southbay injectors. Im thinking of ordering from them. About $150 for a set of 24lb (for 350), not sure what the 19lb injectors go for, Im sure the same. Anyone else use the southbay products?

 

this is a good thread, and im witnessing the same symptoms. figured it was the egr, but it runs good and strong when its nice and cold outside or its not very warm..but when it warms up thats when it just wants to fall on its face, bog down, stall out and idle horrible...

i think im going to get readings off of mine as well and see what numbers i can pull up. im sure the injectors from that 89 engine i swapped in are done for.

one thing i want to ask it would bad injectors throw a code or a check engine light?

 

I'm seriously considering buying a 1991 Camaro Z28, 350, automatic that I found locally for sale. Seems like a good condition car but it is suffering from the symptoms discussed here. Sounds like fuel injectors from what everyone is saying on here. I'm teetering on whether to purchase the car knowing it has this issue, and then get into troubleshoot this problem.

I looked into places to purchase and costs for replacement for injectors (and I'm looking at the places mentioned in this thread as well). I saw the different #lb ratings. What is the recommended for the 5.7L 350 and what are the differences/advantages/concerns with using different #lb injectors?

Thanks,

Ryan

 

How much for the Camaro and what condition is it in?
305 (5.0) call for a 19lb injector, while the 350 (5.7) call for 24lb injectors. If your motor is stock, then go with these numbers. From what Ive been told on this site, larger injectors with a stock motor setup would just be a waste of fuel, and youd run extremely rich. Evidently they already run rich from the factory. So you can start upgrading your motor (headers, high flo runners) and run stock rated injectors with no problem. Do a search on injectors and TPI threads and double check my info. This site has an unbelievable amount of knowledge wrapped up in it...
Good luck, and dont decide against buying that car just because of the injectors...less than 500 bucks to fix...talk the guy down at least that much!

 

If you have a voltmeter, it's really easy to check. Unplug the injectors, check the resistance, plug them back in.

My car was backfiring badly and it turned out literally half the injectors were bad. I got my new ones through the Fuel Injector Connection link. The guy there said the OEM GM injectors from this era are crap and he won't even service them. Once they go bad, get new ones.

Pat

 

I am currently at the halfway point of changing my injectors (bought bosch 3 reman from south bay 22#) and have a question about fitament. I have never installed gas injectors before only deisel. Had to sell Cummins (12.47 @111) due to a second kid, Anyways the factory ones in this iroc fit snug and require a little effort to seat in the bung. However these NEW BOSCH Ones require little to no effort to seat,and 1 literally falls to place No soap, or vasoline req. IS THIS NORMAL? i just dont want to reinstall everything and find a vacum leak. I will check for fuel leak first with just ignition. And yes i read the tech article on how to install injectors. That is why I am asking, there is no satifying pop and they are 1/8" taller even when seated no difect fit. Any experienced advice would be great. As this is now my summer fun car and Winter is finally over here in Alaska and im DONE driving my 00 4x4 ranger(winter beater) and just gave this a major tune up and tranny. Just hopeing this is normal so i can finally drive it.
Thanks , Jason

 

Just an update FYI: I did purchase the 1991 Camaro Z28 5.7l that I was considering and discussing above yesterday. It's my first 3rdGen. Was able to negotiate a price (down about $300). I'm hoping I got a good deal but don't want to know if I didn't...

It runs great for the first few minutes, then loses all power, and idles horribly. I have ordered a set of bosch III injectors and am anxiously awaiting their arrival so that I can get them installed and start to enjoy this car!

Thanks for the advice and wisdom on the injectors. I'm an excited new owner waiting like a kid at Christmas for parts to arrive. Thanks for the insight Pairof91rss and slow305.

I'm sure I'll be back for more advice and tips.


Thanks,
Ryan

 

Ryan, just to let you know, Ive only had my third gen's for about 2 months. This site has tons of good advice, as well as a lot of good people associated with it. Sometimes people go off topic a bit when you ask questions, but its usually with good intent. You can (and will) learn a lot from this site!
Have you checked your RPO's yet? Open the little lockable storage compartment in the rear hatch, and you'll see the RPO sticker. It tells you all the stuff your car came with. You just have to look up the RPO codes. I for one am interested to see what you got man...Congrats to the newest 3rd gen owner, you're in for a lot of fun!

 

i have the same prob. (91 350 tpi). i have changed plugs,wires,checked timing,tps position seems to be ok.. egr fine too. mine will jump from 500 to 1000. really annoying. i have to agree w/ this being the injectors...mine are stock and surprised they are working at all w/ what i have heard.
also if anyone could tell me if that would cause the cruise control to make the car lurch foward and back going downhill. all the vacuum hoses have been replaced on the cruise res. but sometimes it wont hold a spd either though. it just slows down........any info would be cool. (hoping its inj. too)

 

I assume that your problem with "lurching" downhill in cruise control is injiector related. My car does same thing. When its under load, seems to be fine, but when I idle or take my foot off the gas, then the lurching starts. Cant afford to get the injectors yet, so I cant give you an update on the fix. Anyone else having this problem, please let us know if it is fixed with new injectors!

 

Pairof91rss (and all),

I did start to research the RPO codes last evening and was pleasantly surprised. Pretty much everything I could have wanted seems to be in the car. I'm still new to all of this so I can't quickly rattle off which ones are the biggies so... Although this thread is probably not the place, I'll post all of them here since we've started discussing it here and since you asked (in case you're interested):

AC3 AJ3 AM9 AR9 AU3 A31 A90 B18 B2L B34 B35 B84 C49 C60 DC4 DG7 D34 D42 D5X D8F D81 E5Z E9Z FE2 GU5 G80 G92 IPC J65 KC4 K34 K68 L98 MD8 MX0 NA5 NP5 N10 N64 N96 QLC T96 UB3 UQ1 U1C U62 VAN VK3 V73 Z28 1AY 1SD 10Q 10U 11P 6ZW 7ZW 73C 73I 739 8NL 9NL

Thanks,

Ryan

 

Hello all,

Thank you everyone for all of your feedback, it appears quite a few others have had this issue and/or are resolving it (good news for me, means creating this thread was worthwhile for others as well)

Just a quick update... I did order the Bosch 3 Inejectors from Southbay and they should be on the way. I plan to put them in once they eventually arrive...

I will post back and let everyone know the results, hopefully it will help others down the road...

Thanks again everyone

 

SRRF, best word of advice on replacing the injectors is to read the tech article here on this site, it pretty well covers the install. Also when you get your new injectors check to make sure they are same length from oring to oring as mine were different and I needed regular bosch 3's without the adaptor for length. Southbay is sending the shorter ones on monday. I also cant wait as my car is currently apart waiting for the new parts. PS. you should also put an adjustable fuel pressure regulator fuel filter and new diaphram on while your at it. I got mine from tpis, and it is of good quality. If you have any questions just post back as i am in the middle of this myself. btw these are alot easier to install than deisel injectors. The hardest part was taking the runner off on the ac side.

 

Woo-hoo! Success! Thank you all. Fuel injectors were the issue. Finished the install tonight and went out on the town with the new ride.

Installed bosch III's and it took just about 6 hours just like the tech article on this site says.

Thanks,

Ryan

 

Good Job Ryan, glad to hear it, good luck with that new car!

 

OK Ryan, wanna know how she runs. Where did you get your injectors and how much they cost...all that **** lol
Congrats on the car, now lets see some pics buddy!

 

She runs Great! Never had a car with this much power... Had a powerful speedboat with a 454 ci in it once, but never a car. Difference between night and day with the new injectors. Laid down some rubber today.

I ended up getting the injectors from Jon at FIC (no offense to SouthBay) with complete gasket set for about $190. Jon was awesome to deal with. Felt like we were old friends after talking to him. I spoke with him last thursday night, called him back Friday to order. He shipped them the same day - Friday. I received them on Monday. He even took my call after hours on his cell phone when I had a question about the fit. He was just great to work with.

Without further ado, here are the pics:
http://s703.photobucket.com/albums/w...view=slideshow

~Ryan

 

Ryan, just got a chance to check out your car on photobucket. NICE FIND...
That is one good looking car, and I dont even like white! LOL
Cant wait to see some more.

 

man congrats i cant wait to get mine ordered and done.

 

Hello All,

I have obtained my injectors (Bosch III's) and have installed them today. The article on the site was certainly helpful. However, things didn't quite go as smoothly as planned.... There was a leaky injector when I tested the fuel rail with the ignition ON (pressurized the system). I was stumped after checking everything over, so ended up calling Southbay (where I had ordered them from)... they were open on a Sunday (mother's day!) and extremely helpful! Was going to call back and thank for the assistance but got caught up in the re-installation.

So for anyone who may be looking to do this project, just a quick word of advice passed on to me, if you run into issues... I ordered the Bosch III's for the 305 TPI (same length oring to oring) however; they didn't have a spot for the stock clip and seemed to fit rather loose. I have always put the injectors on the fuel rail first, and then plopped it down onto the manifold. Where in fact, this was the INCORRECT way of doing it in my case. When I put them on the fuel rail first, the injector slid too deep and the oring/top of the injector allowed fuel to pass.
So essentially to counter this I put them in the manifold and placed the rail on top, tightening the 10mm bolts on (allowing the fuel rail to slide over the injectors to the correct spot/depth). This word of advice came from Southbay and was extremely useful. Just be careful that everything is lined up before tightening, otherwise you may rip an oring.

This is backwards to the way I have always done it, but it made perfect sense once I heard and saw why it's done this way. The fuel rail slides down onto the injectors until they are snug (preventing them from going to deep and allowing fuel to pass). Not sure if this is news to anyone but thought I'd let everyone know.
The stock clips aren’t used for my Bosch III’s, as once again Southbay stated that the pressure holds them in place (news to me as they seemed rather loose/unfitting).
I have never dealt with aftermarket injectors before so this may be all old news to everyone, but I figure if one person runs into issues and stumbles upon this post maybe it’ll help

The car runs quite nicely, more “kick” and certainly runs smoother. The issues of jumpy idle still exists, however now my SES came on and is telling me it’s a Code 32 (the dreaded EGR code)… never came on before... I have had issues with my EGR system from day 1, but the injectors did help for sure! (I'm sure if the EGR system was functional it would be running like new, definitely smoother with new injectors)

Thanks again for everyone’s help, greatly appreciated (including Southbay!) and now to figure out my EGR system!

 

Would anyone recommend or event think that the Trickflow 24lbs Injectors would be a better buy then the Bosch III's....?
Just a Curious question.
I have a '90 Iroc-Z with a 5.0L TPI and I'm having Isues. I changed the Cap & Rotor, Ignition Module, Coil, and Spark Plugs thinking that would solve the problem. That didnt help so then I changed the Knock Sensor and MAP sensor. After that I found out that the Timing was off. Every time I set the initial timing to 6 degrees like the specs ask for the car runs beautiful with full power for about a mile or so then it gives and runs like crap all over again. The computer advances the timing for some odd reason. The computer isn't throwing out any codes NO matter how much of a rough idle it has. Now the car wont turn over at all and after cranking it over so many times trying to figure out what's wrong, I fried my starter solenoid and I waiting for my replacement. I'm looking for any other sugestions as well.
Also, Do any1 have any idea of what this Beige thing is in this picture ...? It's located behind the fuel tank


Attachment 199497

Attachment 199499

Attachment 199498

 

Sounds like the same problem we were experiencing. New injectors were the ticket for me. I don't know anything about the TrickFlow injectors but everyone I spoke with on here as well others who know injectors all recommended bosch. Have you found a better price on the TrickFlows? Most of the places that offer rebuilt Bosch's have great prices compared to even new OEM injectors.

?? as for the beige thing. Looks like some sort of breather but don't know why it would be on there in a pressurized fuel system. ??

 

I was just curious about the Trick Flows.... They're $259 so I was just curious if its worth the extra $60...
I dont have any idea of the beige thing either but its there with a bracket to support it so I'm pretty sure it came stock with it

 

trick flow, racetronix, summit, accel, are all the same injector. They are disc type made by Standard Motor Products with a different label// All hard to tune. Get some Bosch 3's From FIC but, get the 19lb ones not the 22

 

Just a heads up, I would start a list of items to change starting with the injectors and prepare to have to move down through that list. I have the same problem, injectors did not cure it. It seems to be a very, very common problem with multiple contributing factors.

 

I have the same problem with my 89 5.7 . Looks like i will be purchasing some new injectors as well. This must be pretty common.

 

If the symptoms are exactly the same, then I'd say that'll probably fix it. I had these exact symptoms and ever since swapping out the injectors with bosch III's, the car has run great!

 

Ok... So I got the engine running again... The gave me a knock sensor for a 350 instead of a 305. After changing MAP sensor, External Coil, Cap & Rotor, Spark Plugs, Ignition Module, and Fuel Filter, still have no luck on what causes the timing to advance after setting initial timing at 6*. The odd part is that sometimes it'll advance the timing and sometimes it'll retard the timing.... I'm stumped on why the random adjustments. I followed the instructions from the Chilton's Manual on he Timing adjust process but still NO Luck... Any Suggestions would be greatly appreciated

 

maybe you guysd can help me with mine n tell me if replacing the injectors would fix this. I have a 87 iroc 305tpi. The car was running rough and had little power, would stall out in gear and at stop signs. I set the timing to 6 degrees and it helped a little but it is still lacking power. I want to test the injectors and make sure they are the problem before tearing it apart. so far Ive replaced plugs, wires,cap and rotor, and fuel filter. I had the car running and unplugged one injector at a time. when i unplug injector #3 and #6 there is no difference in idle. If i unplug the others one at a time theres a difference in idle. I also have a gas smell in the oil. Could this be the injectors?

 

I think that would be a yes to it being the injectors.... After all this exchanging parts and tryin to contemplate on what could be wrong with my car, I was convinced to go ahead and take it in to the Chevrolet Dealer in my city.... 4 days, 2 different technicians, and $320 later the only thing that they can come up with is the injectors. He says I have 2 injectors that only read 10 ohms, 2 injectors that read 16.8 ohms... and The other 4 are at 15 ohms which are supposed to be within specs. I dont know if they're right or wrong but if it is I and everyone else on this forum should go get ASE certified and become GM Technicians.... I'm jus saying

 

WOW! I didnt even think about checking my injectors. My 91Z (5.7) has under 70K miles. It just started getting rough at idle when it warms up. Looks like I will be checking mine out and I will keep in mind the Bosch III Injectors.

 

As an update, I changed Fuel Injectors (Bosch iii"s), EGR Valve, Fuel Pressure Regulator, and Oxygen Sensor...... STILL NO LUCK.... Rough Idle, Poor Performance, and Hesitation..... I'm completely lost on what to do with this car... Honestly anymore money spent and I could of just went out and bought a rebuilt

 

I had same problem, replaced my IAC and Coolant sensor and it fixed it. Could also be your Cat. converter if its hesitating a lot.

 

is it true the guage will jump right before you start the engine if the sensor is bad?? (coolant) and was there any other sign of cats being bad??

 

I Just got my injectors in the car (Bosch III). I just need to get my plenum back on. Hopefully Im good then. Just a question for anyone. My problems started almost exactly around 180 degrees everytime. My plug wires and distributer cap were very white from running lean. Is this the same for others with injectors that fixed the problem?

 

I just got My car back together after about a month or so. It runs awsome. Thanks to this post and a few others I caught myself before I spent too much on replacing sensors. A new set of Injectors, O2 sensor, fuel pump relay and it drives great. the only thing I have is that if you get the injectors that dont requirer the clip to hold them into the fuel rail. Dont out them in the rail first. I had only one leak when finished. I removed it and put it back in. No Leaks!. Thanks Guys.

 

Can someone give me a direct link to the tech article on how to do this install of new fuel injectors? Can't seem to find it. Thanks. Want to know what I am in for.