Hulkamania

Hey guys I just got home tonight with my 88 Iroc. Its the 350 TPI and Im having some issues with the way it runs. First I thought it might just have been the fuel cause he said it sat for over a year so the fuel cant be any good in it. On the drive home if I let it come to idle really fast it would die on me. I got it home, drained all the fuel in the tank, replaced the fuel filter and put fresh gas in it. Now it does seem to run and idle better however there are a few issues. The car wont start if I just turn the key I have to touch the throttle as if its carbed. One time it was idling it would drop to 600-700 rpm and bounce between that and 1000 rpm continuosly. What do I need to do next to take care of this? There has been a few times that the service engine soon light has came on but it doesnt stay on contantly. Do I have a coolant temp switch bad making it think its gotta choke? The temp guages stays cool, normal driving range around 180.

CreepingDeath94

iTrader: (4)

Any time one of these cars sits for any length of time, there are a plethora of issues that can cause poor running issues. Fuel pumps don't like to sit in crap gas un-run for long periods of time. I would check your fuel pressure at prime, idling, and if you can under acceleration/WOT. Fuel injectors on these cars are crap from the factory. With age they only get worse. They are inconsistent to say the least from the get go...I wouldn't do it right away, but a lot of these problems stem from bad/leaky/clogged/dead injectors. Try and ohm them out and do the tests, but if you have spare money do yourself a favor and upgrade the injectors now and save yourself headache down the road with other issues related to bad injectors. If it sat, a number of sensors could be out of wack/sticky.

TPS, MAF, IAC could need cleaning/replacament. Again, try testing anything before you just replace it if you can as it tends to add up just replacing parts that are potentially good just to have the same issue...just giving you some things to look at here.

I would also just try and run a few tanks of good clean gas through it and make sure the issues don't just go away with some running...a sitting car is the worst thing for it. Some things may run themselves out if it is crappy gas related.

Check your fuel pressure though as soon as you can as lean running motors are a bad thing ad can hurt it if run hard too long with a lean running condition.

Hulkamania

So what should I check for if my idle is extremly low now? Theres no code being thrown, I cant start it without giving it gas, it was starting with just hitting the key and starting and running fine, but now its idling so low its dying on its own. Still go with the fuel pressure? Can you tell me what my pressure should be primed and then running? I do need to do a tune up though, it smells EXTREMELY gassy so as stated I probably need to think about injectors.

Thanks

burnout88

Sounds like the injector nozzles are leaking fuel into the motor. Get a fuel pressure guage and connect it to the test port on the fuel rail. Check your fuel pressure with the car running. Then shut the car off with the guage still connected if the pressure bleeds down to zero. The nozzles in the injectors are shot.

CreepingDeath94

iTrader: (4)

Or the pump is bleeding fuel back into the tank...your pressure should be around 40 psi at prime/idle I believe. Start there.

vetteoz

iTrader: (13)

On a TPI , having your foot on the throttle WHILE cranking shuts off the injectors because computer thinks you are trying to clear a flooded engine which is what you have if the injectors are leaking down.
The fact it starts when you stop the injectors shows it has too much fuel from somewhere.

You are not giving it gas , you are taking away fuel, see above
EFI works opposite of carb.
Pumping the pedal with a carby sprays fuel in;
with injection there is no squirter to add extra fuel so all you are doing is adding extra air and if enough throttle, cutting off the fuel flow from the injectors

Hulkamania

Well that makes sense however I put the fuel guage on the shrader valve tonight and everything checked out extremely well. Key on no start it goes up to about 30-35 and holds, might leak down to 20 after a period of 5 minutes. Start and running around 40 psi, I didnt rev it I just let it idle and checked the fuel pressure and it held. I shut the key off and it dropped to 35 and held for quite sometime AND the stupid shrader connection on my guage leaked SOME so I know that effected the guage on leakdown pressure. So UNLESS the injectors decide to act differently Im assuming they are ok, as well as the fuel pump. I think I just need to get to driving it and see if it will clear out better.

On another note I have an LT1 94 Z28 and I know that changing the plugs on it is easiest by dropping the Y-pipe is it the same with the L98?

Thanks

BigWhiteGTP

No, it's a tad easier than changing LT1 plugs and I have a dual cat TPI car. I hated changing plugs on my Lt1.

Like Creepingdeath said above, drive a few tanks of gas, maybe even get some fuel injector cleaner in there and some water remover. Also, do a tune up, o2 sensor,distributor cap/ rotor, plugs and wires, and do the MAF and Fuel Pump relays, fuel filter, set the timing right. My GTA ran like junk when i first got it. Even after all that it still ran goofy. We tested the computer and it wasn't even reading the o2 sensor. Replaced the computer and it runs like a champ now.

When it's running good, it will seriously feel like a whole other beast. Good luck.

Hulkamania

What do you mean do the relays? Change them out for new ones?

Hulkamania

Oh and what is the correct timing for a L98? Is there a computer wire you have to unhook if so where is it located?

vetteoz

iTrader: (13)

6 degrees
Vette shown but same connector

vetteoz

iTrader: (13)

Pull the codes ; that will show you if any of the engine's sensors are bad or not reading right .Only need one bad essential sensor for engine to run like crap

burnout88

As stated pull the ECM codes, use this tech article as a guide. On your car jump pins 5 an 6 together.

https://www.thirdgen.org/service-eng...ht-error-codes

Hulkamania

Ok I just pulled the codes on the car and am in need of some assitance in knowing what they mean. I got 3 sets of 1-2 codes which is suppose to be normal correct? Then I got a 3-4 which Ive read is the VAC sensor voltage being incorrect? What is the VAC sensor, where is it located and what do I need to do to fix it? What kind of problems would this sensor cause?

Thanks

Hulkamania

Or is that a MAP sensor error? Im sorry I dont have the book Im having to look it up online. My same question applies though.

Thanks

Hulkamania

Well this should be causing my rich condition correct? What do I need to do just replace the MAP sensor?

BigWhiteGTP

Hulk, in that picture posted up Vetteoz, that circled timing circuit is in the same location but instead on the passenger side in our Fbodies. And that black rounder thing right above it in the picture, with part of the circle crossing it, that is one of the relays I was talking about. It is on the driver side. There are 3 of them, same part number at AutoZone or Checker.

Code 34 is tricky at first for first timers. 90-92 its for a MAP sensor, but for 85-89 cars, code 34 is for the MAF sensor. I'm betting with those new relays I'm telling you about, in place, that code 34 will be eliminated. This could be causing the rich mixture. If not, try and get an actual real time scanner and see what the computer is imputting/outputting in realtime. That is how Brian (Burnout88) found out about my bad ECM.

Hopefully with a tuneup and new parts, your car will run like a champ. If not, the next code will pop up.

Hulkamania

Would it be possible for you to tell me those part numbers?

Hulkamania

Hey man I went out and looked on on the driver side firewall I see 3 relays. 2 are exactly the same and the third closest to the engine is a little different. Are you saying to change all 3 of these?

BigWhiteGTP

I'm sorry, there is 2 of the rounder ones. But the Autozone part# is 912210, just order two of them.

Hulkamania

So you would mess with the relays before you would touch the MAF sensor itself?

Hulkamania

That part number didnt work for me. What is the name of the relay?

vetteoz

iTrader: (13)

The MAF setup has a system where it applies power after you turn engine off to heat up the sensor wire in the MAF to burn crap off.
If this does not happen , the dirty wire will not read correctly = bad performance and MAF error code.Relays are cheaper to replace than MAF

burnout88

The 3 relays on the firewall are called

1. MAF Power Relay
2. MAF Burnoff Relay
3. Fuel Pump Relay

They are wired to together so it is best to replace all three. Just go to the autoparts store and tell you need those three relays. After you replace them reset the computer by disconnecting the battery. Actually disconnect the battery before replacing them. It is important to do the reset by disconnecting the battery.

Code 34 MAF indicates a problem in your air/fuel mixture. Does not necessarily mean the sensor itself is bad. Can be a tricky code to diagnosis as several problems will set it off. Below are some of the most common

1. Bad Fuel injectors
2. Bad TPS or misadjusted TPS
3. Bad Relays (the ones we are telling you to replace)
4. Bad ECM
5. Bad MAF Sensor itself
6. Short in the MAF sensor wiring
7. Vacumm leak

Start with the relays first and do a tune up on the car. Pull the plugs and let us know how they look in color and if they are soaked in fuel.

Let's start there.

Hulkamania

So Im guessing the MAF relay is the ones that are identical? And the fuel pump relay is the one furthest to the left "closest to the engine"

Hulkamania

I bought and replaced the 2 MAF relays on the firewall today, they didnt have the fuel pump relay in stock for me to change it out. However by the battery there is another relay that looks exactly the same as the 2 I replaced is this another one I should change out? I unhooked the battery and swapped them out, the first time I started it the car started fine. After I shut it off and went to try it again it cranked and cranked and cranked and cranked and then finally started what would cause this? It hasnt done that again since though.

Im thinking I am having a plugged cat condition as well, the cat makes alot of rumbling sounds like its got alot of backpressure on it.

I have yet to get around to plugs and wires, is the best way to do plugs from underneath the car? What plugs would you recommend for BEST performance?

Thanks again

burnout88

Yes, changes the plugs from the bottom. Once you jack up the car and crawl under you will see the plugs are not hard to change. These cars run the best with Delco, Autolite, Accel U-groove, NGK. For wires I recommend MSD and an MSD cap and rotor.

No Champion plugs, and no Bosch plugs!!! Also, stay away from platinum plugs. Just run good old cooper plugs.

You really need to do the tune up next and pull the old plugs to figure out what is happening. If you post a pick of the old plug tip next it will help figure out what is going on with your mixture. Since you do not have a scan tool we have to do it the old fashion way.

The long crank can be caused by alot of things, move on to the tune up next.

The cat should not be making noise. Drop the exhaust if you have a chance and see if you take a look inside.

Also, do you have a multimeter? I need you to do an ohm test on the injector coils.

Hulkamania

What should the ohm be on the injectors? Do you think even with the fuel pressure check I did that there is still something wrong with the injectors?

I havent been around very many L98 cars but the ones I have been around I know would LAY IT DOWN if you hammered down from a dead stop. My car wont turn the tires from a dead stop so I KNOW its in dire need of some tuning. I know the L98 wasnt a huge hp motor but it was torquey and Im wanting that TORQUE back! Something I have noticed about this car though is that say I hold the car in 1st and really romp on it something in the rear passenger side of the car seems to hit, or bang. Ive checked the tranny mount on the crossmember and its fine, checked the u joints and they are fine, the only thing I can figure is that its the crossover tube on my cat back is this normal? I do think that my shocks/struts are shot on the car would this cause that to happen?

I really need to get the tune up down with a little luck I will get to it tomorrow if at all possible. The car did its dying crap on me again tonight driving it. It will drive out fine down the highway at 1800 rpm, but on idle it will sometimes die, and it does idle kinda rough so I need to get them plugs and wires changed.

Thanks for all the insight and tips

Hulkamania

Nevermind the ohm question I see that you are wanting me to prove that they have resistence and not blown out.

vetteoz

iTrader: (13)

You are checking to see if injector resistance is within specs and if one or more are low.Low injector resistance can drop the whole injector bank out. Should check cold and hot values. Injectors coils can go bad when they heat up

burnout88

Correct, the injector resistance should be between 16 to 17 ohms on bosch injectors and 12 to 14 ohms on mulitec injectors. Most 88 model year cars have the bosch injectors. 89 and up tend to have the mulitec injectors. The fuel pressure test only checks the nozzles for leakage and not the injector coils.

burnout88

Also you say you checked the tranny mount. Visually they will often look ok and you cannot actually see the crack in them. The only way to check it is often to remove it or you can try and put a jack under the tranny near the tail shaft and lift up slightly and see if the mount separates. It sure sounds like a broken tranny mount.

Just a side note, please fill out your profile info with your car's year, model, engine, tranny, and axle info if you know it. It's helps us all help you and prevents redunant questions from being asked. Location info is also very helpfull since certain parts of the country devlop certain problems. I am in AZ so we have a problem with rubber and plastic vacuum lines dry rotting from our high temps.

Hulkamania

Well well check this out. Number 7 plug wire was completely off the 7 plug so that would explain the rich smelling gas, also the rough idle, low power, and hard starts. I got my plugs changed wasnt too bad at all. The 1,3,5,7 of course 7 was clean but they were clean in comparison to 6 and 8. 6 and 8 seemed to have more of a white build up around the electrode. Im heading back out in the shop here in about 10 minutes to replace the cap, rotor, and plug wires then I will take it out and see how she runs. I pulled down my exhaust and saw that the rear honeycomb in the cat was just rattling around so needless to say its out of therw now. I didnt know that these cars had an air pump tube that connects into the cat itself. Also I checked the tranny mount and I believe you are right, I think its broke I can see a crack in it so something else I need to fix. Im sure glad this car cosmetically and body wise is in such great shape other wise it wouldnt have been such a good deal. An 88 with 74,000 miles on it though thats pretty rare, I just wish the P.O. would have been alot kinder to the interior. The seats are mainly what I hate about it. I have some new seats on the way from ebay though they are some JDM type things, they look pretty sweet hopefully with the Sparco brackets they bolt right in and look nice.

Anyway thanks for all the insight and tips. Also can you tell me how to set up my profile?

Thanks

vetteoz

iTrader: (13)

In the red bar at top of page (LHS )
User CP
https://www.thirdgen.org/forums/usercp.php

Your Control Panel
Go to edit my details

burnout88

Sounds like your making progress, Excellent!! Since the cat is falling apart just punch the hole thing out. It’s going to keep failing apart and is probably stuffed up in the front. You can replace it later. Keep us posted on how it runs.

To update your profile info when you are logged just go to the top of the page and click on the User CP button (it’s next to the home button). Once in there click on edit details and fill out some of the basic info on the car.

Hulkamania

The car is coming around nicely as far as how it runs. It starts/runs/idles MUCH smoother and MUCH better than it did before. It no longer smells like RICH fuel going out the exhaust which makes sense with the number 7 cylinder plug wire being off the plug. You should have seen the corrosion that was on the cap/rotor/and plug boot ends it was unbelieveable. I have no idea how this car ran as good as it did with how neglected it was. I will NEVER AGAIN buy plug wires that you have to make up though, it takes too much time getting the boot on the wires!!!!

For now Im going to put some tanks of fuel through it, injector cleaner and probably some lucas injector lube type stuff eventually. Then onto interior cosmetics. Seats on the way. I also noticed my struts are SHOT! This car is a work in progress!

Hulkamania

Ok the tune up HAS NOT helped the starts of this car. I am starting to wonder IF the injectors are just leaking fuel down into the cylinders and causing it to be flooded out, cause when its warm it starts up fine. Cold is another story. Any advice?

GOATS2QUICK

iTrader: (5)

back to some of the prior posts, you need to check (ohm) the injectors, including the cold start injector.this will tell u if the are bad.

Hulkamania

what and where is the cold start injector

GOATS2QUICK

iTrader: (5)

if you have it, it is one the drivers side, by the fuel rail, in between the rear runners on the tpi. looks like the other injectors, only used to cold start, but it could leak as well. check all injectors.

i have a question, can you hear the fuel pump prime and shut off when you first turn on the ignition switch?

Hulkamania

Yeah the fuel pump does seem to work fine, hearing it and also using the pressure gauge.

GOATS2QUICK

iTrader: (5)

okay, we know fuel pumps delivering to the rail, youve confirmed good pressure at the shrader valve.
you need to check the injectors next, this will confirm, or eliminate the flood problem.
if they check out good, then procede to the tps switch, and make sure its adjusted correctly.

Hulkamania

Well I cant find the 9th injector and my freaking ohm meter has disappeared! SUCKS!

burnout88

If the car is an 88 it has a cold start injector. Heres a pic of it.

http://www.chevythunder.com/cold_start_injector.jpg

I recommend you read through a lot of the links on this page below, start with the section with the swapping TPI into an older car. It's will education you on the whole tpi system and it's parts. About 5 or 6 pages in is a section on the TPI sensors and injectors. You will be a TPI expert after you read through the site.

http://www.chevythunder.com/

Hulkamania

Im REALLY getting irritated with the starting of this car! It just does whatever the heck it wants. This morning it was probably in the upper 30's low 40's and sat outside all night. She started right up this morning no problems. I get home from work today and it was raining, around the same temp probably 40's I go out to start the car crank crank crank crank crank crank crank crank crank you get the picture. Cycle the key off and on, the fuel pump primes everytime. Its not throwing any codes now at all since I replaced all the relays. Tempature has EVERYTHING to do with the way this car starts and its really ticking me off. If it was the injectors ohms wouldnt the car do it everytime or at least be more consistent? As of right now I have no way of ohming my injectors since obviously my fluke meter got stolen. Is there any other ideas of what might be causing this?

Hulkamania

I just checked my fuse panel and I noticed that my 3 amp crank fuse was missing. Would this have anything to do with my cold start woes? From my understanding that controls the cold start valve?

vetteoz

iTrader: (13)

No ,
the injector coils may be going faulty when hot. (common problem )
Only way to confirm is ohm them out hot and cold to see if there is a difference. A low resistance in one injector will cause the ECM to shut the whole bank down

Hulkamania

Well then I need to be buyin me a new fluke meter cause Im sick and tired of the way this car starts! So that fuse being gone wouldnt cause any problems? If it is the injectors that means replacing all AND the cold start injector as well?

Hulkamania

Say it is my injectors what lb injectors would you recommend? 19? Or would it benefit me to do something else? Southbay has some great prices on 19 stockers.

burnout88

Interesting, with that fuse gone your cold start injector will not fire so you will not get the extra fuel you need for a start. Someone, probably pulled it because you have a short (very low or no resistance) on your cold start injector. You need to get that meter and start testing injector coils.

350 cars use 22lb injectors.