I’ve searched and read a lot of useful information here, but I could really use some guidance based on my specific issue from people far more knowledgeable than me. Thank you in advance for your help.

A few months back I bought an 86 iroc in pretty decent shape. I noticed when I bought it that it ran and drove well, aside from a high idle when in park or neutral. No big deal I thought to myself, I’ll be able to figure it out, assuming it was a vacuum leak…

first thing I did was replaced the IAC valve. No change.

then new oxygen sensor. No change.

Sure enough, I did a smoke test and found a massive vacuum leak where the drivers side runner meets the lower intake manifold.

Once I removed the runners I found the cause of the vacuum leak to be the previous owner replaced the gaskets, however, he didn’t scrape off the old gaskets. Wow.

then I figured while I got this thing apart I might as well replace some other stuff while I’m at it, so I replaced the thermostat, plugs, wires, and put on a pair of hooker shortys, shiny new valve covers..

Once I got it all back together and it definitely runs better, but the idle problem persists. I should be a little more specific. It’s not just a high idle issue, it seems to be ok for a little while, and once it gets up to temp the issue gets worse and won’t start unless you give it some gas, and then it will die when you shift from park or neutral to drive, unless you rev it up and drop it into drive. It also seems to be way down on power when in this weird state.

Tonight I learned how to read the check engine code using the paper clip trick, and it’s code 45 (Oxygen sensor rich).

ok so at least I know it’s running rich, makes sense based on how it behaves…but I don’t understand WHY it’s running rich.

maybe the MAF sensor is bad? But that’s an expensive part and I don’t want to replace it if I don’t need to. Is there anyway to test it?




Here’s another strange thing, I noticed there is a sensor between spark plugs on cylinder 1&3 which isn’t connected to anything, I looked everywhere and I can’t find any plugs or wires hanging either. Upon further research I learned this is a coolant temp sensor. could this cause the engine to run rich somehow?

Can anyone post a pic showing what kind of plug is supposed to be connected to this sensor? And which harness do the wires run from? What color are the wires that I need to find?

 

What a terrible night to have a curse.

No, that CTS is for the gauge. Wire might be green. Seems like a datalog might be able to uncover some clues about what's going on.

 

Thanks. Please excuse my ignorance, what exactly do you mean by data log? Is this something I can do myself or does this require someone with necessary equipment to read what he ecu is doing in real time?

 

You can do it yourself, with the necessary equipment. I use a cable like this one:

https://boostednw.com/Datalogging/gm...-gm-datalogger

And hook it up to my phone with the ALDLDroid app. It can also be hooked up to a windows pc running tunerpro or tuner cat.

 

The gauge sender in the cylinder head requires a connector like this one linked below. It slides easily onto the flat round tip of the sender in a perpendicular manner.
Coolant Temp. Gauge Sender Connector, 89-92 TPI, 89-92 TBI (tpiparts.net)

The wires in the harness have little to no slack and only reach as far as the part they connect to, so if that connector is still hanging around in there, then it's not likely to be far from the sender.

 

Thank you for the info, I was able to find the green wire with the connector still present, Connected to the sensor and my temp gauge works now.

 

How are your injectors? are they the originals?

 

Brand new injectors a few months ago, along with a new gas tank and fuel pump.

all I know for sure is that the car is running rich (confirmed by code 45), high idle in park and neutral, sometimes will die when shifted from park or neutral into gear unless I give it some gas and essentially “neutral-drop” it. Also very bad hesitation when accelerating, especially from a stop, if I give it to much gas it almost completely dies, and in a few seconds it’s recovers and will lurch forward with tons of power. Most of the time it feels like it has hardly any power, just bogs down so much.

So far I’ve replaced the following:

-intake gaskets
-throttle body gasket
-O2 sensor
-Idle air control valve
-coolant temp sensor for the ecu
-throttle position sensor
-pcv valve
-cap and rotor
-spark plugs and wires

I finally got a vacuum gauge and checked yesterday (because this seems like a classic vacuum leaks problem), but from what I’ve read on this forum my 20” vacuum is right on the money for where it should be. Correct me if I’m wrong about that.



so now I’m suspecting a fuel pressure issue (sounds like that’s what you’re getting at as well).

renting tester to check fuel pressure today. Maybe fuel pressure regulator is bad allowing too much pressure through?

what about the MAF? I can tell you that when I unplug it the engine dies. So in theory it’s working, but maybe it’s reading incorrectly. I wish I could test it, I hate just throwing parts at this thing not know what the actual cause is. Especially something as expensive as the MAF which I can’t just return if that doesn’t fix it.

More suggestions and advice welcome and appreciated!

 

Update: I just checked fuel pressure, I have no idea what to make of this so please let me hear some opinions.

with the key on/engine off I have only about 15psi. I’ve ready in other threads this should be 40psi?




with the engine idling it looks like about 36psi to me, which should be correct, right?





What does it all mean? I assumed if I had too high of fuel pressure it might explain running rich….but if my pressure is too low, then would it run lean?

 

Oof, parts cannon'd. Did you follow the instructions in the factory service manual for resetting the IAC and TPS? Have you tried following the diagnostic flowchart for Code 45 in the factory service manual? Did you install a heated o2 sensor to compliment your header install? Sorta sounds like things get worse in closed loop. 36psi with regulator vacuum connected is ok.

 

The FP should be 43(WOT)-35psi. 36 at idle should be normal. Your IAC is the main control of the idle and I see you replaced it. Did you do the IAC reset? Even if replaced it still needs resetting. There is a how to on the home page for this procedure. Also check the TPS voltage at idle, should be about .54 volts when the throttle is closed.

What injectors did you use? 305 and 350 use different flow rates and the brand matters. You may need to tune the engine to the specific injectors you used.

The O2 rich code. Don't fixate on this, a massive vaccum leak will cause a rich condition so this code could be stored from when you fixed this issue. Clear the ECM of it's codes and see if it comes back.

The low FP at key on could just mean the pump relay is not running long enough to bring the pressure up before start.

 

I did follow the procedure I found on this forum, but I don’t have a factory service manual, unfortunately. I bought a Haynes manual which is completely worthless and doesn’t show any procedures.

I did install a heated O2 sensor.

It’s important to mention that this problem existed before I replaced anything, and I have not noticed any difference since.

shouldnt I have fuel pressure with the key on and engine off? I just tested it again and I have 0psi, no pressure without the engine running

 

Can you hear the pump 2 second prime now that fuel
press is zero ?

 

I did the IAC procedure, but I’ll try it again now.

also I’ve read the tps procedure, but what I can’t figure out, how do I check the tps voltage of the connector is plugged into the sensor? I tried sticking my probes in the back but I can’t seem to make a connection to actually read it

 

As for the injectors, the previous owner installed them right before I bought the car. He gave me the old ones, but I don’t know what he installed.

here’s an interesting but strange clue… I just unscrewed and lifted up the air box where it attaches to the air filters and the engine died, and will not restart. Why wouldn’t it run, it’s not like the engine knows the air isn’t being filtered…

and another clue, I flipped this air box snorkel over and I can see that there are some gaps where the top and bottom come together, looks like maybe there was a gasket of some sort in there when it was new. Going to seal up all these cracks with some rtv and see what happens.






still shouldn’t matter though which is why I’m scratching my head, maybe that little bit of extra air is messing with the MAF readings.

any ideas?

 

use sewing pins and push them through the wire coating so the go into the wire itself. Put your probes on the pins.

 

good call 👍 going to try this tonight.

thanks

 

I just read some different treads regarding bad EGR valves might cause my symptoms..

I mentioned earlier that the wire that is supposed to plug into my EGR isn’t connected, but I was under the impression this wouldn’t affect how the engine runs. Can anyone clarify this?

 

Wow this thread skips around a lot, the egr temp switch will not cause running issues but will throw a code 32.

 

😂 you got that right! Cool, thanks for the info.

slowly losing my mind trying to figure out why this turd won’t run right. I’m running out of ideas, maybe my ecu is just bad? Would I be an idiot if I just said F it and went carbureted instead? Half kidding and half serious at this point

 

BTW that sewing needle trick was next level 🙌 worked great, got the tps set correctly going to take the car for a spin and report back

 

Thank you, learned that one from my High School shop teacher Dr, Hux.

 

Welp unfortunately the mystery continues, what in the world is causing it to run rich, I just can’t wrap my mind around what I’m missing here.

I’ve read a little about the ninth injector (cold start inj)…is it possible that it’s always on and just dumping fuel when it shouldn’t be?

I see that it’s common to delete the cold start injector, I read you can unplug it and use a block off kit because it isn’t connected to the ecu at all…but how to people block off the fuel line that runs to that injector?

 

Can anyone tell me what this unplugged connector is for? Drivers side under dash fuse panel location

 

Below is a pic of where the fuel line for the 9th inj. hooks to the fuel rail. You can get a cap nut to cap that connection off. You may need a chip burned for cold starts if you remove this.




IMHO you are on the right track with thinking injectors. After injector swaps I'd say it's a 50/50 chance of them being tuned properly and most cases they engine runs rich. Your injectors are a mystery. Are they for a 305 or 350? are they even GM injectors? Flow rate? This is what I feel is missing here. The flow rate for a 305 is #19. 350 injectors flow @ #22. If you have a 305 and the OP put 350 injectors well there is your rich condition. You may be at the point where datalogging the ECM is the next step.

 

Thanks for the info. What exactly do you mean the injectors being tuned properly? Is this something I can check?

also I really would like to do some live data logging. I can’t justify buying a laptop and cable and software that I most like won’t be able to learn how to use…Doesn’t anyone sell a scan tool that I can plug In to the port and see the live data?

 

I've only been casually following this thread and am no expert (although I do play one on TV), and I agree with the above comments about more information needed on what injectors are in there. We really have no idea if they are even right for the car. It is also very common these days for people to install Bosch III injectors which don't typically work right without some computer tuning/adjustments.

The whole air filter removal/engine dying piece also seems like a very important clue, UNLESS it is causing something unrelated like accidentally unplugging the MAF while removing the air filter housing.

 

How’s this for a coincidence? The name of the guy I bought the car from is Aaron R. At first I was like is this dude trolling me?! Then I see you’re in Missouri 😂

Anyways I called Aaron (previous owner) yesterday to hopefully get a little more info. He’s a total stand-up guy and his honesty made me comfortable enough to take on the project, so I bought the car. He told me everything before I bought the car, but there was a ton of info we discussed and I just couldn’t remember everything. Luckily he didn’t mind speaking to me on the phone yesterday.

this car has a fascinating story (still doing a little detective work) but I’m excited to share what I know in a whole separate thread, should make for an interesting read.

I’ll try not to write a book here, but long story short, about 1 year ago Aaron rescued this car from a scrap yard just before they were going to crush it. The car had been sitting since around 1996 I believe (last time it was registered).

When he picked it up the intake plenum, runners, and injectors were in the trunk. Someone had removed them at some point.

Well after sitting for so many years, the tank and pump/lines, injectors were frozen solid with nasty crap. So he put in a new gas tank, fuel pump, lines, and injectors.

He bought a full set of OE used injectors, which I can verify by the part number on them compared to the old ones which he gave me as well. He did test them to make sure they all worked properly before installing them.

He didn’t do anything with the fuel pressure regulator. (I think this is an important clue)

He got it running good, but it had this same high idle/hesitation issue that he wasn’t able to figure out either. That’s when I bought it.

I have some new updates since I’ve been trying to diagnose this…i think it’s the fuel pressure regulator. In my posts above when I tested the fuel pressure I should have zero with just the key on, and 36 when idle sounds too low, doesn’t it? Maybe that’s as much pressure as the busted regulator can hold?

shouldn’t I be seeing closer to 40-45 psi at idle?

then I thought, what is the purpose of the vacuum line on the regulator that goes to the plenum? If the regulator is bad couldn’t gas be sucked directly into the plenum causing the rich condition?

Is there any way for me to be certain that the FPR is bad?

 

The plot thickens…

Heres some new facts-

-I decided to verify how rich I’m running, I burned though 7 gallons of gas in 30 miles. That’s 4.3 mpg. 😬

-I think the fuel pressure tester I rented from oreillys was leaky trash, I could tell it had been rented by probably 9,000 idiots before me. I bought a new tester at Harbor freight, very different results.

This is with Key on (no start) fuel pump prime. 42ish psi…Good right?




I wanted 10 minutes to see if my regulator was losing any pressure, and it’s a little over 40 psi still…that shouldn’t be bad, right?




so what exactly does this mean? Doesn’t this rule out my bad regulator theory?

Also I was thinking maybe leaky injectors before this, I figure if my injectors were leaking I’d lose pressure quicker.

regarding my injectors-

here’s the original injectors, all have the part # 5235301



And here’s what they were replaced with (hard to see but they all have the same number)




I’m running out of ideas.

How about I up the ante a little bit here? I’ll buy a case of beer for whom ever gives me the suggestion that turns out to be the smoking gun. If you’re not close I’ll send you a gift card or Zelle you some cash for the beer so I don’t need to ship it 😂

 

This is all making less sense by the minute, I just went through the small box of misc parts the previous owner gave me (mostly spare lug nuts)…and there’s an additional bag containing 7 injectors. The part # on these ones is 5235047.



here is is compared to the 5235301, the tips are very different from eachother.




I see vastly different info all over the place. which injector should actually be In my 1986 Iroc 305 tpi LB9?

 

These are the injectors that should be in your car:

https://www.southbayfuelinjectors.co...injectors.html

Have you tried smoke testing the intake for leaks? There's machines for it, I did it once by smoking a joint and exhaling into the fresh air PCV tube.

 

Thanks, but regarding the injectors I posted above, can anyone tell me which one of those part #’s would have been installed at the factory? Based on my google searches I see various info claiming each of those to be OE part numbers, but they are clearly different parts.

yes the first thing I did was the smoke test, which revealed leaks where the runners attach. I replaced the gaskets and have since retested confirming no vacuum leaks now. At idle I have 22” vacuum.

just retested the fuel pressure from priming the pump and turning key off, longer test this time.

In 20 minutes my gauge dropped from 42 psi to 31psi. Does this mean my injectors are leaking?

 

Doesn't matter what injectors came from the factory; they're all bad now and should be immediately discarded. Your fuel pressure seems pretty similar to what mine does, I wouldn't suspect leaking injectors.

 

Right, I’m not asking which of these 37 year old injectors I should install. I agree, they’re all garbage.

the reason I would like to know which one originally came in the car is because I’m trying to determine if that’s what is causing my current issue. If they are the wrong injectors that would explain why it’s running so rich, and I will immediately order the ones you linked above.

I don’t desire to spend the $500 right now if that isn’t what’s causing my issue.

 

I pulled a spark plug just to see what it looks like, these plugs are brand new (less than 100 miles).


is this what people mean when they say “wet” spark plug? It’s not literally wet to the touch, it’s more of a sticky kind of varnish.

any thoughts?

 

If it is injectors not cts or maf causing the overly rich condition.
might want to invest in a datalog cable or mt2500 scanner.

https://www.southbayfuelinjectors.co...injectors.html

 

thanks, what does cts stand for?

also I see that the injectors you linked are different than the ones posted by Komet a few posts up. Any reason why one would be better than the other? Obviously I’d prefer to buy these cause they’re half the price, but I don’t want to regret it later.

 

just started following this thread. Sounds like a nightmare.
It doesn't really sound like the injectors are leaking....however they are definitely crap. Checked the part numbers on both sets....one set flows approx 19lb the other set flows approx 20lb. Either one would be appropriate for a 305. Try checking the resistance on them both hot and cold. Can also check the cylinders....if any of them are wet...you have a leaky injector...
With regards to replacement injectors any of the 19lb injectors we carry will be just fine. People are extremely happy with the bosch injectors be it the bosch gen ll or the bosch lll's. On occasion we do hear that a tune is required with the bosch lll's however that is not an issue we run into on a regular basis. They delphi's are a great injector as well. Direct fit and from what we hear they do not require a tune although they are much more expensive. Keep in mind if you want a set of injectors you receive 10% off at checkout for being a tgo member. The code is tg11

 

thank you for the info! 👍 Btw I called you guys earlier today, I don’t know if I was speaking with you or someone else but the guy was extremely helpful, definitely the type of place I like doing business with.

 

not a problem....you probably spoke with Frank. Really hope you can get this figured out....if there is anything we can do to help please let us know. I'll be following the progress! Can't wait to hear the outcome...

 

After looking at my plugs and checking the oil a few times I’m starting to think I have gas in the oil. I wish I knew for sure but it feels a little thin to me and I can’t say it smells exactly like gas but it doesn’t smell like only oil either. It smells like the rich exhaust fumes…so probably gas.

I think my next step is a leak down test. I’ll post the results afterwards.

 

Those plugs are nasty rich, put a new set on your purchase list. If compression was the primary problem, you'd be having a lot of blue smoke but it would probably be running better than that. All signs point to massive overfueling, datalog would likely indicate something out of balance.

 

Thanks.

Regarding data logging; I’ve read so many threads referring to the proper cable and tuner pro etc. Is there any links you can share where it dumbs the process down enough for me?

Also, can I use any laptop? All I have is a newer basic HP with usb/hdmi ports, latest windows, no fancy graphics card or anything. But from what I’ve read it sounds like I’m supposed to have a laptop from when John Denver was still kicking, and running windows 94. RS232 ports, floppy drive and all.

And then there’s the software, am I actually going to be able to figure out how to use it? I’ve just been through it in the past and I hate buying stuff that I can’t get to work right.

 

Datalogging was mentioned post 4
might download tuner pro rt or even winaldl
the 1227165 is picky to connect to . Drops connection and won’t connect . Winaldl seems to work better on 86-88 and tuner pro rt for 89 tpi maf.
cables in the classifieds as well. You need to put the ecm in 10k mode to start data flow then connect to the program. It’s a usb to aldl cable. Works with win 98 on up.
I have win 11 works fine.

 

I am an older guy with no experience with the whole datalog thing. I was able to figure it out with a little help from youtube videos on how to initially set up TP RT. Your computer should work, I think Tuner Pro RT works on a newer computers now. My laptop runs windows 10. TP RT is free to download so you will just need a cable to purchase. You should be able to download the proper "mask" for your engine combo. This gets loaded into TP RT. Unfortunately with these OBD1 systems this is really the only way to properly diagnose what the hell is going on with the engine.

 

Buy the Moates cable, NOT the Red Devil. I bought the Red Devil and regretted it.