THE CAR RUNS FINE FOR LIKE 20 MIN ITS GET WARM AND THEN THE RPM START TO GO UP AND DOWN WHEN I STOP ITS DOING IT AND GOES UP TO 3,000 AND STAY THERE

YES I CLEANED THE THROTTLE BODY INTAKE MANIFOLD IS REALLY OIL COLOR INSIDE

I CHANGED IAC,TSP,COIL,SPARK PLUG,WIRES, MAF SENSOR WHEN I CHANGED IT DIDNT WANT TO START BUT IT STARTED DONT KNOW IF it’s the WIRE TO THE MAF

HAVEN’T CHANGED IAT

I FEEL LIKE THE PCM GETS HOT CAUSE IT RUNS FINE AND THEN ACTS UP AND I HAVE TO WAIT TO IT GETS COLD AND IT STOP

NO MULTIMETER TEST HAS RAN

PREVIOUS OWNER SAID THE FIRST OWNER BLEW IT HE REBUILT IT DONT KNOW IF ITS TUNE PROBLEM


PLS HELPPPP

 

Why did you post in “Podcast”? There's a notice at the top of the page indicating “Please do not post in Podcast forum”. The Podcast was shut down many years ago when the original owners sold the site to Internet Brands. It was never a place to post technical problems.

I’ll move this to “LT1 Based Engine Tech”.

ADMINISTRATOR

 

How long ago did the P0100 (MAF) and P1361 (ICM) codes set? Do you still have both codes? Any other codes?

Did replacing the MAF clear the P0100 code? If not, you need to check the wiring harness for the 12 volt reference signal at the MAF harness connector? If there is a failure code with the MAF circuit or sensor, the PCM should default to the speed-density mode and the engine should still start and run reasonably well.

Have you done any replacement or testing for the P1361 code?

Scroll down to ICM harness:
4th Gen LT1 F-body Tech Articles

A reliable multimeter is essential to troubleshooting these issues.

I see a similarity with another case of extremely erratic RPM surges. That turned out to be a defect in an MSD Optispark, a problem that apparently affected a significant production run. What brand is the Opti? How old is it?

Please clarify what this means - “PREVIOUS OWNER SAID THE FIRST OWNER BLEW IT HE REBUILT IT DONT KNOW IF ITS TUNE PROBLEM”. What “blew” and was rebuilt…… the entire engine, or just some component like the MAF?

 

CAN YOU TELL ME WHAT TO CHECK TRYING TO DRIVE THESE WEEKEND @Injuneer

I KNOW SOMEONE THAT IS A ELECTRIC GUY FOR A DEALER SHIP

SO CAN YOU TELL ME STEP BY STEP SO I CAN SHOW HIM WHAT TO CHECK WITH THE MUTLI METER FOR THE PROBLEM IM HAVING

 

BOTH SENSORS ARE NEW EVERYTHING I NAMED FOR FIRST POST IS WHAT I CHANGED AND IT DIDNT DO NOTHING

codes been on since nov 30 codes are still on after i changed both senors

i try to earse them and when i do i try to turn the car on and

it doesnt want to start but the third try it does when i turn it on the check en light flashs one time

he rubilt the whole engine

havent done the. Multi meter test to the harness

do i check the maf sensor and the icm / harness

can you tell me what to check for the problem i know someone that does electrical work with cars so i can tell him what to check with the multi meter

 

I actually gave you a link to checking the ICM in my post #3 above. You have to read the responses carefully, and follow up.

For the MAF, there are three wires in the harness connector - yellow (variable frequency signal), pink (12 volt+), black/white (ground). Key on/engine off, connector off sensor, check for 12 volts between the pink and black/white wires. There is a fairly common problem with failure of the pink wire somewhere in the harness. But that is primarily 1996 models, not so much 97.

Engine running at idle, use multimeter with a frequency range to measure frequency between the yellow and black wires. At normal idle speed should be 2,000-2,500 hz. If you are having idle RPM surges, frequency will rise and fall with RPM.

It is not likely that either of these codes is causing the RPM surges, but get rid of the codes to rule them out as contributors.

You need to download a (free) copy of the 1996 factory service manual. It is 99.9% the same as 1997. It has detailed descriptions of the codes, and a logic tree for troubleshooting the code.

https://www.mediafire.com/?40mfgeoe4ctti

You have to be a bit more patient. You sent your first private message on Christmas day, and spending time here was the last thing on my mind.

You also need to kill the “caps lock”. Generally not acceptable, because in Internet protocol it is considered to be “shouting”, and rude.

When I get more time today, I have a lot more questions to ask about your engine, modifications, the tune, etc..

 

Did anyone do any diagnostics before replacing parts?


When did the problem with the idle surge start? Was it that way when you bought the car, or did it start surging after you drove it for a while? Did it start at the same time you found the codes?

Does the car have a manual or automatic transmission?

Are you saying that when you turn the key to start the car the SES light flashes once, then goes out and does not come on again? Or does it flash after the engine starts running?

What are you using to scan for codes?

Did he rebuild it totally stock, or did he make any modifications - heads, cam, exhaust, etc.? If changes were made, did he have it tuned for the changes?

I answered those questions in post #6.

What does the front of the Optispark distributor look like? Is is red?

I have diagnosed an RPM surge problem in the past, and it was caused by the cap on an MSD Opti. Appears the red epoxy insulation on the cap failed, and there was cross-firing between the wires inside the epoxy that connect the inside cap terminals to the plug wire terminals. That spark was interfering with the cam position sensor module, and sending an extra pulse or two every once in a while that the PCM interpreted as a sudden increase in RPM. So in response to the false higher RPM pulses the PCM opened up the IAC valve to keep the engine from stalling if the throttle suddenly closed at (false) high RPM. At idle, the engine would surge in excess of 2,500 RPM. While driving, it would raise the RPM and hold it there. All this leads me to believe you may have some sort of spark/high voltage interference on the high and low resolution pulse signals from the Opti to the PCM.

Over what range does the idle surge when the engine is idling? What about when driving and the engine is operating the car?

Alternatively, have you checked the throttle blade return spring to insure the throttle is fully closing when you let off on the accelerator pedal?

 

REFRESH
this is what is going on with the car when i bought three months ago it was okay i was driving and driving nothing wrong with it till nov 30 th didn’t change nun just oil

I was doing donuts/burning out when i was doing it mid way it started to hop and the check engine light came on and i stopped and the rpm out of no where went up and stayed on 3,000 rpm

drove home went to autozone to check what codes popped up it was p1361 p0100rpm

after that i checked the codes are icm and maf i changed both sensors and the rest is on post 1 the rest i named i changed those sensors to see if it would make change of the rpm from going up and down but it didn’t

no one diagnosed it. checking engine light came on i went to auto zone and checked on my own

trans is manual

the rpm can stay high on 3,000 and i can put it to gear and the rpm drops and keeps going up and down if i stay steady in gear if i stay for long the rpm goes up and stays as well

when im on gear while the rpm going up and down for me to go i have to press the clutch and bring up the rpm by 2,0 or 3 for me to go or not it stutters to go on low rpm

when im driving it like that i come to a stop the rpm goes up and down and then it goes up to 3,000

so the car what is doing the rpm goes up and down and then goes up stays on 3,000 and doesn’t come down

OHH and i connect the tablet and force the rpm to come down but it kept with rpm going up and down but didn’t go up there

optis would check tmr to see the color i think it a black cover

can i share a video so you can
see

i try to erase the codes and when i do the car doesn’t want to start the first time but starts the third time with the check engine light on again i tried the disconnect battery thing and doesnt want to start the first time but does the third time with the check engine light on with still the same codes

if i repeat my self sorry

 

Did your friend with the multimeter check the MAF and ICM circuits?

Did you check the throttle cable and blades to see if they are sticking?

Does the car have the optional traction control (ASR, RPO NW9)?

 

no we haven’t

traction is asr

 

"no we haven't" what - not checked the sensor circuits...... not checked the throttle blades..... all of the above ? ? ? ? ?

OK.... I know "traction is asr", Camaro called it ASR, Firebird called it TCS..... does your car have traction control or not? Yes, or no? There are three cables involved that affect the position of the throttle blades. Appears whatever is causing the idle in RPM control problems occurred while you were abusing the vehicle.

 

yes it does have the traction control button ASR i can turn it off or turn it on

while this problem is going on with the codes i have and the rpm going up and down out of no where there was like twice when i would drive the car the abs and the abs inop would be on the cluster and i wouldn’t have no traction control even if i tried to turn it on or off

but afterwards the abs inop never came on the cluster and i can turn traction on or turn it off now

havent checked the circuits

i have moser 12 bolt posi

 

Was ASR turned on when you were doing donuts and burnouts? Did it respond to the loss of traction at the rear wheels?

The system is “ON” when the engine is started. The switch turns it “OFF”. From above comments appears ASR currently working when you try a burnout? Does the Moser 12-bolt have the two ASR reluctor rings and wheel speed sensors installed at the ends of the axles? The 4-channel sensors have to be ordered as an option with the Moser 12-bolt.

At this point you may need to have the EBTCM module scanned for codes.

3rd request - have you checked the throttle blades and the cable for sticking, or looseness?