Okay guys. What could it be?

[coupe]

Car still pings when 1) at operating temperature and 2) over about 1/4 throttle (or under load up hill).

It runs fine and hauls ass when it's still cold, but once it gets up to normal temp...I have to be very judicious with throttle position. It's driving me nuts. Here's what I've replaced:

O2-sensors,
TPS,
plugs (colder too),
wires,
distributor,
fuel pump,
filter,
MAF electronics (itsa C&L),
Checked resistances in ACT and CTS...they're within normal.
Tried different gas-stations and fuel injector cleaner...nada.
Also have retarded base timing to 8...still does it; just runs hotter.
The Balancer is a sealed SFI fluid piece.

It started doing this gradually over a weeks-time after I changed to an electric fan. :think: Car didn't show hot on gauge, but I wnet back to clutch fan instead...no help.

? ? ? ? Sorry to bring up this old topic. Does anyone have a ProM for 24# injectors I can try? That's about the last thing it could be :shrug:

[86GT]

Try unpluging the CTS (ECT) sensor and let it fail. The EEC will default to something like 210 and see if that helps. Just by doing a simple resistance check is not enough. This also applies to the ACT sensor.

[coupe]

Okay, I have unplugged each. separately. then started car. no different.

Checking the EGR vacuum (EVR) next to see if it's working. Found out the EEC will lean mixture if it senses the EGR is open...maybe it's sticking open and the thing is leaning a bit much :shrug:
The ping I heard today was definitely a lean-"crack" sound...head gaskets still there tho :(

[slvrbullit]

I have that 75mm ProM that is called for 30's that I am not using.

[86GT]

The EGR will create a lean condition as you stated. Not to sure what the EEC does if it senses a bad EGR. Try disabling it in the tuner. I can not remember, do you have a Tweecer. If so can you datalog?

[QWKSNKE]

The EGR will create a lean condition as you stated. Not to sure what the EEC does if it senses a bad EGR. Try disabling it in the tuner. I can not remember, do you have a Tweecer. If so can you datalog?


no he does not

[86GT]

Just thinking out loud but if an injector is stuck open, the EEC will sense this and try to lean out the mixture causing the rest to go lean.

I would also try running a cylinder balance test.

[LeeH]

EGR is not functional except at part throttle cruise, Idle and WOT are not effected unless the EGR valve is stuck.

[Dale McPeters]

EGR is not functional except at part throttle cruise, Idle and WOT are not effected unless the EGR valve is stuck.

Correct one attay boy for you...now get back out in the garage
and get that car finished up.....:jester:

[jwillburn119]

hey, check inside your distributor... all the way down to the hall effect sensor, and the CPS sensor... it is inside the distributor... so you might have to take the distributor off... just a thought... thats what mine was doing and i tore it down... 3 times in a row.. because of it

[coupe]

New distributor. Accel Billetech.
Troubleshooting the EGR:
I unplugged EVS (EGR vacuum solenoid) and car wouldn't start. Reconnected it, started car, and hooked direct vacuum up to EGR & idle drops, then bumps back up normal & runs fine...exhaust smell is a bit less "rich" too doing this.(computer is doing what it needs to). Pulled codes again & of course, got the EVS (since I had unplugged it). I happen to have a new one so I replaced it anyway (this valve controls the EGR function).

No change. :nono:

Tommy, I will be trying that ProM...might have to come across some "freebie" 30#ers too. Just happen to know where some are.

[LeeH]

New distributor. Accel Billetech.
Troubleshooting the EGR:
I unplugged EVS (EGR vacuum solenoid) and car wouldn't start. Reconnected it, started car, and hooked direct vacuum up to EGR & idle drops, then bumps back up normal & runs fine...exhaust smell is a bit less "rich" too doing this.(computer is doing what it needs to). Pulled codes again & of course, got the EVS (since I had unplugged it). I happen to have a new one so I replaced it anyway (this valve controls the EGR function).

No change. :nono:

Tommy, I will be trying that ProM...might have to come across some "freebie" 30#ers too. Just happen to know where some are.

Well Dale and I were talking on the phone and he suggested using a breakout box to watch sensor voltages. There are a few things though that dont sound right, The car should still run without the EGR sensor plugged in and the rough idle should continue with vacuum applied to the EGR valve(EGR open). This of course introduces spent exhaust gas into the intake which is for all purposes mostly inert gas which causes the rough idle. Unmetered air is another possibility, EFI is nice but it has a way of masking certain problems.

[Dale McPeters]

Well Dale and I were talking on the phone and he suggested using a breakout box to watch sensor voltages. There are a few things though that dont sound right, The car should still run without the EGR sensor plugged in and the rough idle should continue with vacuum applied to the EGR valve(EGR open). This of course introduces spent exhaust gas into the intake which is for all purposes mostly inert gas which causes the rough idle. Unmetered air is another possibility, EFI is nice but it has a way of masking certain problems.

Yep it should still start with the EVP/EGR unplugged.
Just stepped out to the shop and tried it out on the
blue car, it started fine. Of course the engine light
came on and set codes.

By the way coupe I think it is broke....:jester:

[LeeH]

Yep it should still start with the EVP/EGR unplugged.
Just stepped out to the shop and tried it out on the
blue car, it started fine. Of course the engine light
came on and set codes.

By the way coupe I think it is broke....:jester:

There ya go trying to break the blue car again:jester:

[coupe]

True. But it was the EGR vacuum solenoid unplugged that made starting difficult. Unplugging EGR sensor doesn't do anything but throw check engine light and sure-enough, doing that showed up in the continuous memory as a code 33. And opening EGR causes idle to drop, but then stabilize...my understanding is when it opens, it senses that & leans out?? but maybe thats when cruising :shrug: ?

Another interesting code today from "continuous memory" is 96. Fuel Pump Secondary circuit failure. EEC not sensing voltage on Fuel pump monitor circuit. Could this have "deteriorated" suddenly? Could this cause the problem? NOt even sure what this is doing.

I went ahead & erased the CM memory. Maybe it will try to adapt to something tomorrow.

I'm about ready to see what a carburetor costs these days. :nono:

[coupe]

I had another thought. When setting my TPS, I shoot for .99v on idle, but if I reference the "ground" to the frame, I get lower reading than if I reference ground to say throttle-body or something closer to TPS. What is causing this? The values are the same if key is "on" but car is not running... Why is reference to ground different when running? If I referenced the wrong one, the setting would be around 1.15 instead of .99 :mad: I'll see if it works. That sounds like a possibility.

[86GT]

Code 96 is sensing the return voltage from the fuel pump relay. I had this when I did the SD to MAF conversion. I had to run a wire from the fuel pump relay back to the EEC. I can not remember what pin it was but if you would like I can look it up.

If the car runs then the obviously the pump and relay are working and it would be the feedback.

There should be no difference on the reference. Check pin 60 on the EEC and the ground strap on the back of the motor. There should be a big ground strap going from the drivers side head to the firewall. There should also be another ground wire on the same lug for the O2 sensors.

[QWKSNKE]

could the fuel pump be going out?

[coupe]

I will check ground. I thought pump was the problem earlier. It's got a new pump & filter. No change.

The TPS voltage thing didn't do shit. It's not a TPS adjustment. Seems like it's not timing or fuel delivery; I've checked about everything. I'm really leaning toward EGR. I'm gonna block it off. Or get an LS1.

[93Cobra#2771]

Just hitting on the obvious that hasn't been mentioned:

• Are you SURE you don't have any vacuum leaks? Have you checked recently, including your inlet ducting?
• Any exhaust leaks PRIOR to the O2's?
• What is the mechanical condition of the motor - does it burn a little oil, or have a lot of miles on it? (possible carbon deposits/hot spots/preignition?)

[coupe]

Have checked for vacuum leaks...will check again.
Exhaust buttoned up pretty well.
Very good condition, it's probably got 150k miles, but very good condition, no oil consumption, smoke, or such. Last time i had intake off, there was a bit of carbon on a couple intake valve heads, but not too bad. The thing is generally running beautifully...hauls ass until it's at operatiing temp...then I have to be soft with it...that's the only catch. What would cause it to only be doing this at operating temps...ie: when the engine is warm (CTS reading above like 170º)
And I'm too afraid to see if WOT solves the issue...it is doing it only at part-throttle...but so badly that I'm afraid of head-gasket problem by flooring it.
WOT when it's still cool --> runs fine great, no missing at all.

[slvrbullit]

I know you installed a new dizzy, but did it come with an new TFI module. The more I think about it and I just read an article that the foxes were notorious for TFI gettin heat soaked and after getting to operating temp causing crazy drivability issues.

A friend of mines car would run and then all of a sudden just quit. After the car sat for about 15 minutes it would start right up. Replaced the TFI and the problem went away.

[coupe]

New TFI on there...it ran no differently with a new distributor and TFI...and all the other stuff I've thrown at it...
Thankfully I've not spent a fortune on this problem yet...gotten the "hookup" on most of the stuff...

[93Cobra#2771]

I don't think it would be the TFI or it would be doing it at times other than just WOT.

What about the 10 pin connectors - have you had them apart and checked for good connection? They can cause all sorts of odd things to happen. It's a good idea to go through them and spread the male connectors apart with a nail or pin so they'll get good contact.

Have you pulled a plug or two just to see how they look?

[coupe]

yea. Read about the 10-pins somewhere. They are in great shape. Not dirty, good looking connections, etc.

Again, this thing is doing this pinging about 1/4-throttle...less if going up a hill, so it's definitely in the load calculation. MAF? :shrug:

[QWKSNKE]

. MAF? :shrug:

I would be willing to bet that it is

[93Cobra#2771]

That's what I'm starting to lean toward as well...

[coupe]

Connections to MAF look good. I do have the filter directly on the meter because the idle surged with the cold-air elbow...but it also pinged with the elbow on there; I tried that already. Why would a stock-electronics MAF degrade suddenly?? I cleaned the tiny sensor elements. They are not prone to internal electrical failure are they?! :shrug:
I hate to buy a new one when I'm going to Speed Density later anyhow.

[QWKSNKE]

Connections to MAF look good. I do have the filter directly on the meter because the idle surged with the cold-air elbow...but it also pinged with the elbow on there; I tried that already. Why would a stock-electronics MAF degrade suddenly?? I cleaned the tiny sensor elements. They are not prone to internal electrical failure are they?! :shrug:
I hate to buy a new one when I'm going to Speed Density later anyhow.

Is the auto in the car now? if so, it may have made the symptoms magnify. you couldn't feel it before because the pinging might have only been very slight. With the auto in place it will load the motor up more.

if the auto is not in now, then i don't know

[coupe]

Auto is in now, but it did it bad with 5-speed...no difference. Again, it started doing this around November(?) and I dealt with it during winter, replaced tho parts mentioned, and did the Auto last week.

[QWKSNKE]

Have you tried throwing some octane boost in to see if it will go away

[nxcoupe]

I am certain the mass air is the culprit, causing the load calculations to be way off. I would say the cooler air is causing the computer to give more advance because of the IAT spark adder. It is doing it in closed loop too, so the mass air is my suspect. Try spinning the mass air in the intake ductwork, move it 30 degrees at a time in the same direction even though you have a conical filter. If the pinging goes away, you know you are getting better readings of the incoming air. Right now it is seeing less load, and giving less fuel and more spark accordingly. Good luck. Put that ProM on and see what happens. Also, check the fuel pressure with a different gauge, that happened on a customer's car once.

[coupe]

:banana: I think I fixed it. :popcorn:

We'll see how it does as the day warms up, but it did much better this morning.

[93Cobra#2771]

Don't just tease us, tell us what you did... :slap:

[coupe]

N/M. :nono: Still doing it...not as bad. It's the MAF...trying something else before writing off the C&L.

[snakebit95]

N/M. :nono: Still doing it...not as bad. It's the MAF...trying something else before writing off the C&L.

Hey Coupe,
Are you running an aftermarket ignition? Not to stray you away from the MAF, but I had a similar problem when my car was still EFI. I installed an MSD-6AL ignition box, and started having detonation problems. It took me forever to diagnose the problem to being noise in the trigger wire that ran between the MSD and the coil. I installed some wire shielding around the trigger wire and grounded the shielding to the chassis......and problem solved. Mine always seemed temperature dependant too. It ran good when cold, but acted-up when warm. Just thought I would give you something else to think about.

[snakebit95]

Oh, something else to add.......are you running a cold-air kit in the fender? If so, does it have an elbow in front of the MAF? I had some problems in the past with a MAC cold-air kit that screwed-up the air distribution through the meter. If so, remove the elbow and attach the filter directly to the MAF and see if that helps. I have used the C&L meters with good success in the past, so I know they work.

[coupe]

Yea. I had the filter directly on the MAF to solve the idle-surge problems (up & down hunting until it dies). It idles great with filter on MAF, but terrible air-sampling for the MAF.
The MAC elbow has a longer straight-section of the pipe; I put thatpart in front of MAF. Working much better, but cold-idle is pathetic again.

[LeeH]

Have you tried reclocking the meter in an attempt to help the idle issues?