Hank426

Ok so I have a '90 Camaro with the 3.1 auto. The car starts and runs fine but after it has warmed up, the idle is just terrible. Really low (400-500 rpm's) and just choppy. The car won't stall sitting in park but at a stop light in gear and on the brakes it tries to once in a while. I've also noticed since I've owned the car the exhaust always smells really rich. Not sure if that's related to the problem or not. It also never throws a code for anything. I've read it could possibly be the coolant temp sensor. Any thoughts?????

Thanks

Base91

iTrader: (1)

It could be a bunch of things or a few together. Do you have a manual? Chilton's is OK. It describes all the components related to engine management and how to diagnose problems and test various components. Is the engine all original? Have you done anything to it? Is it well maintained? Start with the usual stuff. You should check the injectors. They are the heart of the engine so if they're no good nothing else matters. You could pull the vac line from the fuel pressure regulator and smell for gas. If you smell gas you need to replace the fpr diaphragm. But if it's original it probably needs to be replaced anyway. Check everything is in good repair and take it from there if you still have issues.

southbay08

definitely check the injectors, anything less than 12ohm needs to be replaced. If they are the stock multecs they tend to shut down when they are hot because of coil failure which is common for those injectors. Might want to check the regulator as well.

Hank426

The car is all stock. I've had it for 8 years, its got 115k miles on it. I only run it in the summer then park it for winter and start it evey few weeks. I've done the tune up stuff like plugs , wires , distibuter cap, fuel filter, and this year a water pump and t-stat. I only put a few hundred to a thousand miles on it a year. How would I test the injectors? I have a haynes manual to it but its pretty much useless.

Thanks

Base91

iTrader: (1)

The Chilton's is better than the Hayne's. To test the injectors take off the upper plenum and disconnect the leads from the injectors. Measure the resistance of each one. As said they should all be 12+ ohms and all close in value. But if it's original it's almost 100% for sure they need to be replaced. See Southbay on this board. They have a good set. Also, as you'll have the plenum off anyway replace the fuel pressure diaphragm.

Hank426

Thanks. if it is injectors what would you recommend? thanks again

southbay08

we have a set of bosch gen ll's. They are a direct fit and we warranty them for 3 years.
If you have any interest we would be more than happy to help you.
Please contact us at any time!

www.southbayfuelinjectors.com
shop: 516-442-4707
cell: 516-492-6504

Hank426

thanks southbay08. Do you have a link to the specific injectors I need?

southbay08

sure do. Here it is.

http://www.southbayfuelinjectors.com...injectors.html


Do not let the advertised application throw you. You will need the same exact injector. Let us know if you have any questions

Hank426

Ok so I finally got to test an injector (the injector for #1, the only one I can get to without splitting the plenum) and engine cold it only had a value of 3.9 ohms and after running the car a bit 3.6 ohms. So I think new injectors are in order. Also going to do the fuel pressure diaphragm while I'm in there. Thanks for the help

Base91

iTrader: (1)

Also, once you get it running again run some Seafoam or similar cleaner in the gas for a while. It worked wonders on my engine.

southbay08

not quite sure that would be a good idea in this case. He is going to install new injectors. If he uses seafoam once they are in, if there is any debris in the fuel system it will flow through the lines and ultimately into the injectors. Just takes a tiny piece of dirt to either clog an injector or cause it to leak.

91rs-t-tops

if and when well i should just say WHEN. Mine go out again ill be ordering a set of them bosh. The ones i got work good but only got a one year war. Three years i can live with that.

Hank426

I've been running injector cleaners in the car for years so I'm not going to with the new injectors just to be safe. I just ordered the set of injectors from southbay, is there anything else I'll need to change them out? I've never messed with injectors so it's all new to me. Thanks again

Jetmeck

iTrader: (3)

Let us know if the injectors fix this. I had a 87 TPI do this and it was covered under warranty way back when. New injectors fixed it.

Jetmeck

iTrader: (3)

?

Base91

iTrader: (1)

Debris is always a possibility but I'd expect the cleaner to disolve anything and not just dislodge it. Also choice. After replacing the injectors and some other stuff and cleaning what I could the car still ran very poorly. It was the Seafoam that got it running really well. It took a while but it got there.

southbay08

I am not saying that seafoam doesn't work,,,, hell..we used to sell it and we put up a post on this forum about it way back when. The fact of the matter is that it all depends on the coniditon of the fuel system and the injectors. You're very fortunate that it worked so well for you. It can also make the problem 10 times worse. We have seen it so many times.

91rs-t-tops

OK so mine is doing the same thing in park no problem in gear choppy idle and die. going down the road runs great acceleration great just at a stop. Im wondering about possible vacuum leak. i gan give it just a little fuel and hold the brake and its just fine not chop no hesitation. My injectors are fine. fuel pressure regulator fine. icm fine plugs good. what about egr could that cause a problem? It dose need a new set of plug wires though. im gonna try to idle it up a hair and check my timing make sure its on. Other than what ive mentioned Not sure right off hand. And i dont have a chiltions or a hanes book to look at on it SO i turn to you guys for some ideas.

Base91

iTrader: (1)

You can't adjust the idle. The ecm does it. However, it sounds like you need to check at least a couple of things. The idle air control valve on the throttle body needs to be clean so pull it apart and make sure there's no build up. Also check the egr valve isn't stuck open. There are 3 valves so make sure they are all seated closed when the car is idling.

91rs-t-tops

Ok will check and let you know what I find but egr dose leak exhaust around bottom. Could be problem?

UK Speedbird

My 3.1 has a similar but opposite problem, mine is a high steady idle of 1000rpm and misfire in P/N, or 850rpm in D, which ends up throwing the expected code 35. I've changed everything including IAC and suspect the only two things left are EGR and a vac leak. Is it safe to pull the connector to the EGR to see if it changes anything, or will it damage the EGR or ECM?

Base91

iTrader: (1)

You can disconnect the egr you'll just get a code. You need to look at the three valves and make sure they are all seated so no exhaust gas can get past them. You can also block off the pipe that goes to the intake to see if it is having an effect. Then when all other issues are sorted it can be unblocked. I made a little metal plate using the gasket as a template. Just don't have the hole in the middle. Have you checked injectors etc. etc. etc.?

UK Speedbird

Thanks Bese

Yeah I got 14.5ohms from all 6 injectors and have a constant 38psi at the rail, but the carb cleaner trick didn't show any apparent air leaks. Not done a compression test though yet but I'm pretty sure she's healthy that way as she runs just fine away from the idle.

Speed.

scury13

Hello, I have a very similar problem. My son has a 1991 RS 3.1. We had several fuel related issues we resolved and now we have this erratic idle and stalling when coming to a stop. I have been through hundreds of threads on here and tried many suggestions to no avail. No clue where to look now.
New fuel pump, fuel tank, IAC, EGR, tank pressure valve, coil, ICM, CTS, ATS, and injectors from Southbay. Only starts acting up after its at operating temp and restarts with no issue each time it does stall.

Base91

iTrader: (1)

To be clear the car will drive ok but the issue is when you slow down to stop and it stalls? If so, try putting the trans in neutral when you're slowing down to see if it makes a difference. Maybe the trans isn't down shifting.

scury13

@Base91, yes it drives great down the road. Accelerates with no issues. As the RPMs come down to a certain point it will stall out or idle will drop then raise, drop then raise and usually stabilize once stopped and sometimes it wont stabilize. Like hunting idle. even does the hunting idle in park after it starts acting up. I did notice at a slow cruising speed around 20 to 25 mph the RPMS go up and down as well.

scury13

Bump, If anyone has any thoughts please chime in. I tried a couple of things yesterday and found that when I unplug just the VAC line to the MAP idle goes up above 1000 and stays steady. If I unplug just the connector to the MAP the idle goes down to about 450 and stays steady.
Both plugged in and car will not idle, MAP tested out fine with VM and VAC pump. Any thoughts?

Maverick H1L

iTrader: (8)

First, the 730 ECM has a "Stall Recovery" mode where it will raise the idle speed to attempt to keep the engine running, which is why the idle speed goes down, jumps, down, up, and then dies. The reason the ECM levels off the idle speed with either the vac hose or the wire connector to the MAP disconnected is because you've set a code and it's operating on a pre-set table, not taking into account certain sensor readings.

Have you replaced the vacuum hoses yet? If you touch one, does it leave black on your fingers? Are the ends of the PCV hose cracked and does the valve seat tightly in the grommet? What is the condition of the brake booster hose? And finally, have you replaced the valve cover and/or any other intake gaskets (valve covers generate a HUGE vacuum leak if they're leaking)?

Also, have you reset the ECM and gone through the idle relearn yet?

Base91

iTrader: (1)

Have you tried putting the trans in neutral when you slow down? It's possible the trans is not shifting down as you slow down and it's stuck in too high a gear. Try neutral if you notice the symptoms. Maybe at least eliminate it as a cause.

scury13

Thanks for the reply guys, I will give a bit more info. We have replaced all VAC lines, plug wires, plugs, TPS and a check valve that I broke pulling off hoses. All VAC lines verified for correct routing. Sprayed carb cleaner everywhere when first started and idle good and no sign of a leak. 3 IAC and 2 different methods of idle relearn more times than I care to admit, lol. No other gaskets have been replaced. fuel pressure at rail is 42 PSI. Tried again today and here is what happens. Car starts right up, idles fine, revs fine. Go down the road no problem. within about 3 or 4 min of starting car issue begins. seems to get worse as temp rises. Swhen reducing speed the idle starts jumping from the 25 MPH mark until it drops below 10 MPH. between that speed is when it will stall out. once below that if it hasn't stalled it will settle a little but still Hunt, surge etc at idle. Always restarts on first key turn. Does it in Neutral as well. Got home and tried the VAC thing again, this time pulling off made no change in the idle. No codes ever show up either, just the expected 12. I also found the ECM is a reaman. It is the correct model and prom but a reman none the less.

9/12. new info. Today the temp outside was down about 15 degrees from yesterday, which was 95. I start the car, idles fine like always on startup. Take off down the road. it took much longer to start having the issue even though the car was at operating temp. However, I could not get the car to stall once, and even though the idle bounced some it never got as bad as yesterday or the other days when it was above 90 out.Heat related ? ICM, changed it out but it was a year ago, Fuel pump, changed out a year ago and pressure checks good at all times. injectors changed 8 months ago but they are remans. haven't rechecked them cause when my first set were bad problem was entirely different (plus bosch from southbay and have not heard any issues with them). Could one if these be failing again?

antares57

iTrader: (8)

I'm in need of a set of injectors for my '91 Firebird V6 3.1. Would this recommended set also apply to my vehicle. Didn't want to hijack. Just wanted to be sure before ordering. Thanks.

southbay08

yes, they would

Base91

iTrader: (1)

If it's temp related what is the engine temp like? Thermostat ok? Have you checked the temp sensor in front of the injectors? That's read by the ecm.

antares57

iTrader: (8)

Engine temp is good. Thermostat changed out not too long ago. Just changed out the FPR cause it was bleeding fuel. Four injectors ohmd to 12.5, one to 5.6 and the other to 10.5.

scury13

No overheating issues, runs about 220, around town if its gets warmer fan kicks on and brings it back down. I did change the CTS out about 2 weeks ago with one from Autozone. I am wondering if it may be the ICM, cheapy from Oreilly's. But would it allow the car to start back up so easily if it was bad? Maybe its a closed loop issue, changed the O2 sensor out not to long ago too. any way to check the readings of these thing at the ECM without a scanner?

scury13

yep, your injectors are bad and need replaced.

southbay08

RBob

iTrader: (1)

This thread is a prime example of failing Multec injectors. And why I continuously post that if the stock factory injectors are still in the engine ('89 - '92, TPI & MPFI), don't bother to test them, just replace them.

Why tear everything down to test the injectors without having a set to put right back in. When the ones in my car failed it was at highway speeds when the engine was good and hot.

The engine would intermittently cut out then come back. Other times it would lose some power and run rough. Those injectors have been sitting on the shelf for years and they all read 12 ohms. But they are still bad.

RBob.

scury13

Agree, Injectors are an easy fix and pretty easy to identify as an issue. Now if only figuring out my idle, stalling issue was that easy.

RBob

iTrader: (1)

Check out this thread:

https://www.thirdgen.org/forums/v6/1...dle-learn.html

Clean the TB as described then do the idle learn. See if that clears it up.

RBob.

Base91

iTrader: (1)

And thanks to Hank426 for the use of his thread!

antares57

iTrader: (8)

Ordered some from SouthBay last night.

antares57

iTrader: (8)

Thanks!

antares57

iTrader: (8)

My '91 V6 3.1 did exactly the same thing. I was 60 miles into a 250 mile journey when they decided to cut out and come back and it eventually died. I managed to get it started and limped it back home at 50mph. Did the FPR test and it failed so I changed that but neglected to ohm the injectors...my bad. Now I know better.

southbay08

antares57 they Shipped out today

Rob, I am in TOTAL agreement with you...it's the same old story with the stock injectors, they are absolute junk and cause so many headaches. I am glad that you made the recommendation to just replace them as it is difficult for a fuel injector company to tell everyone to just purchase another set without it sounding like a sales pitch.

scury13

Seen it, tried it. No luck.
Been out camping for a couple days. Will be back at it again tomorrow though, thanks for the tips.

scury13

So here is what I know, when the temp outside is cool, 70 yesterday, car runs fine. Today it was 85 and car started acting up again. Checking the wiring but still wonder about the ICM. My question is if ICM was the problem would the car fire right back up on the first try. Most references I have seen to ICM being bad is hard start or no start once hot.

Hank426

I have a question for Southbay08 or anyone who might know. I finally got around to putting in the injectors I ordered from southbay (bosch gen II, Fords I think). I noticed that the stock retaining clips from the multecs don't really fit in these bosch injectors because the clip groove is not cut all the way around on them like the multecs.

Do I need to use clips at all? The bosch injectors don't seem like they could move at all once the fuel rail is bolted back down. Another question I have is, is it better to put the injectors in the intake first then put the rail on or just put them in the rail first? Thanks

southbay08

Truthfully, you really don't need them unless you find that the injectors are a little too short and are not sitting high enough into the rail...remember there is at least 45lb of pressure holding them in place so they are not going anywhere. Most of the bosch lll injectors do not need a clip either.
On these injectors it's one half dozen the other....you can install them into the rail or the manifold first. Installation is key with the bosch lll's. They are installed into the intake first then the rail.
If you would feel more comfortable with the clips let me know and i will send you a set. Any other questions give us a shout