I have started driving my 92 RS again after spending most of the last 10 years in the garage. I ran it now and then just to keep fluids moving and prevent rust in the engine.
The car starts and runs decently at idle and low throttle positions but if I go over 20% or so it just bogs and then revs up and bogs. It does not seem to do it at any particular speed. I have driven it on the highway and it will happen there or just going 10mph down the road. To get it going again I have changed the oil/filter/spark plugs and injectors.

Any suggestions on what to look at? I have made a video if that helps, forgive the poor quality. I was cruising down the road at at 7 seconds went to 50% throttle and you can see the revs dive. At 15 sec I take my foot off the gas.

https://www.youtube.com/watch?v=pHcH...ature=youtu.be

 

Most likely cause: stock in-tank fuel pump is shot. It will get worse over time, to the point the engine won't run at all, even at idle.

 

I replaced the pump a couple years back. Still possible I suppose but the new pump has only a couple hundred miles on it.

 

305 tbi right? Hook up a fuel pressure gauge to it, pinch off return line rubber hose, & prime the system. It should hold pressure. It should be around 17-18psi.

 

Depending on what pump you bought and where, there are some truly awful replacement pumps on the market.

Ummmm... have you replaced the fuel filter recently? It's on the driver's side framerail, cylindrical-shaped.

 

Might also check the converter if you don't find any fuel problems.

 

No convertor to worry about.
I changed the fuel filter when I changed the pump and main line.
I will see if I can get a pressure reading. Of choose if it is a blockage issue it would be a flow rate problem. I got a new cap and rotor on the off chance it's that.

 

It could be very weak ignition, but I think the most likely culprit is a fuel issue.

But honestly it could be almost anything. You'll have to do some legwork and rule things out.

 

For those with a similar problem it turned out to be the ICM ( ignition control module ). I got lucky and didn't have to deal with changing the fuel pump again.

 

IAC = idle air control.
ICM= ignition control module.
I've seen ICM's do strange things before, but never just bog out like its starving for fuel or air.

 

I searched the web and actually found a thread on here where someone asked about the symtoms of a bad ICM and the response was would not go over 2500 rpm and would run poorly when it got warmer which matched what was happening to me. Can't find that thread now of course.
I took it out, had it checked and it failed. With the new one the car runs great.

 

You got lucky!!! I have had the same kind of running issue when the little piece of rubber fuel line between the pump and sending unit splits open.

 

Not that lucky. That exact same thing happened to me a few years ago. I thought it was the pump that went bad. Sure enough it was that one inch of rubber that cracked open. The pump was fine but being 20 years old with 110k miles on it, I changed it anyway as pulling that tank out was not fun.
I still have a slightly jumpy tach at idle and it will stall at parking lot speeds when I let off the gas. I still have some work to do but at least it is drivable again. I need to finish a tuneup.

 

When it rains it pours. After working fine for 2 days on my way to work this morning it stumbled and would do little more than idle. I managed to limp it the rest of the way to work but I could not give it any throttle or it would just stumble all over itself. I got a code this time 44. Lean fuel mixture.

 

Further update, the code 44 just sprung up because of poorly it was running.
The ICM is bad again. I tested the resistances/continuity per the service manual for both the primary/secondary coils as well as the pickup coil and they all passed in spec. I am at a loss. Either I got a bad part or something else is causing them to fail.

 

Check your ground strap, negative battery connection and coil/coil mounting for corrosion and proper tightness. A bad ground can easily knock a module out. Some of the older cars also had tach filter that would short out and cause the module to fail.

With all the misfiring and corresponding oxygen making its way through the exhaust the code 44 is not suprising.

 

Checked all of the grounds and coil. All look good.
I decided to get an AC delco ICM hoping I just got a bad part before. I also changed the cap and rotor while I was in there but the new ICM failed 15min into my drive to work.
This is very frustrating.

 

ICMs are so bad these days. I've blown through a few cheap ones and expensive ones... I always get AC Delco or Borg Warner standard ICM's now. Just plain jane normal ones, and they seem to last the longest.

 

Are you guys putting heat dissipation paste between ICM and distributor?
If so, I've read the stuff coming with the Delco ICMs is old and degraded, so you should use regular new paste.

 

I have used the paste for each of the two I replaced. The BW cam with a thinner clear paste which was probably just dielectric grease. The Delco came with a thick white paste. I spread each of them evenly around the mouting surface. When I replace it again I am thinking of ordering some Artic silver from newegg.
Other than datalogging and hoping to see something or just randomly start replacing coils I am not sure where to go from here.

 

Don't know if it helps, but I had a car do something similar before and after chasing my tail it turned out the MAF just needed cleaned and it was instantly back to normal. Something quick and easy to check.

 

This is a 92 RS. I'm sure it's TBI, and even if it was TPI, by 92 they were speed density.

 

It is TBI.

 

I use thermal paste (Arctic Silver) traditionally used between processors and heatsinks in computers

 

I have been searching for answers still. I found this thread: https://www.thirdgen.org/forums/tech...ve-ground.html

It has the wiring schematic for the ICM. It doe not list my car but it looks nearly if not exactly the same. I saw there was a ground on the 4-pin pigtail. I tested in on my car and did not get any continuity between that connection point and the engine or the body. I will track and test it some more but this could be a root cause.

 

Are you looking at the first pic for 87 (165 ecu) or the second pic (730 ecu). The second pic is for 91 and probably 92 such as yours. The ICM is grounded through the mounting screw to the distributor body as shown in the pic. The thermal paste will create a barrier between the ICM and distributor body so a good connection at the mount screw is important. If you have any corrosion between the screw and distributor plate, you will not have a good ground path. You could make a short piece of wire with an eyelet for the ICM mounting screw and attach the opposite end to a good ground point making sure the connections are clean and tight. See if this helps.

 

Al, thanks for pointing that out. I was looking at the first pic. You just saved me from going down the wrong path. This last ICM was pretty well coated in the thermal paste from the mounting screw to the distributor plate but I will certainly check the ground there.

 

Glad I could help. Let us know what you find as this will surely help others who may have the same problem.

 

i've always felt that most of the time when the ICM went out, there had to be a reason. ignition coils can be carbon tracked inside or fail under high loads, so no matter what testing showed on it i always replaced the ignition coil when i found a bad ignition module.
Delco are the only replacement parts i trust.
i also feel the same when the ignition coil goes out, there is a reason why.

 

From what I read Coils usually fail due to poor plugs and plug wires. I have run the engine in the dark, looking for any shorts from the wires but found none.
I replaced the plugs last year with plain copper core AC delcos. The wires are MSD 8.5mm that seems to be in good shape but you never know what is inside the pretty insulator.
Whatever it is, it's probably/hopefully connected to whatever is causing a slight idle bog and fuel smell in the exhaust. I have got to be getting misfires. I will have a week off here soon for Christmas so I will have time to tear into it

 

Update:
I finally got to work on the car.I tracedthe problem down to cylinder #8. I pulled the plug and immediately saw a small gap, I am guessing about .01-.015. I regapped it to .035 and the car idled much better. Now could such a small gap cause ICMs to blow?

 

a tight gap shouldn't hurt anything electrical other than cause a misfire.

the ignition coils can fail because of old age, as can anything.
the insulation on the primary windings can start to break down and cause higher than normal current draw which kills the module. that is why i would replace the coil when i found a bad module.

if the module is still good but the coil is bad, then its normally something on the secondary side, high resistance somewhere in the cap, rotor, wires or plugs. or again it can just be the insulation on the secondary windings breaking down and causing weak output or no output.

when i was doing testing or repairs i would always check for excessively high voltage on the secondary side. i've seen weak ignition coils cause low performance and there wasn't anything wrong with the rest of the system, just a weak coil.

also, anything made can be defective.
one of the times i tuned up my car, just a couple weeks later i started to get a misfire. testing the secondary voltage showed high output on 1 cylinder, the plug was bad. a few weeks later it did the same thing on a different cylinder, another bad plug. when it happen the third time, i replaced all the plugs and its been good since.
later on i read that there had been a bad run during manufacture & some plugs were defective.
figures i would get 3 bad ones all in the same box for my car.

 

Update:
Replaced the ICM with another Delco and replaced the coil with a delco as well. I made sure to ground them both well. Its made a few trips and so far so good. This one is working better than the others. I still have occasional high RPM stumbling but it is not consistant like before. I also still have a fuel smell in the exhaust. It is bad enough that I smell like fuel for an hour or two after being around the car. Things have at least improved. Still needs work though.

 

Have you checked the coolant temp sensor in the front of the intake manifold? When those go bad they'll do all sorts of crazy things. Rich idle is usually one.

 

I checked that coolant sensor as well as the IAT and the TPS thinking one of those may be causing the rich condition, all spec'd out ok though. My gut tells me I still have an ignition issue somewhere. I double checked my engine ground and it is solid.

 

Check the ecm grounds at the back of the heads.

 

Grounds are good. Not sure what that bracket is or what was a bracket attached to the drivers side one is.

 

I seemed to go through an abnormal amount of ICMs for a while. Not as bad as you, but still.

Once I realized the ground for them is through the distributor and engine, I ran a ground from one of the mounting screws for the ICM directly to the firewall, and later when I replaced the distributor completely, I made sure the mounting bolt was clean and contacted the base plate good, and used a hose clamp to hook that same ground wire to the distributor shaft housing.

Perhaps my ICM is finally going out again though anyway and causing my current problems.