Sudden RPM surges - TPS issue

Good morning.

Can you monitor the system and tell me the long term rim reading on the O2 sensor? You could have a vacuum leak not allowing the engine to return to idle.

If you disconnect the IAC, does the idle drop to normal?

Has anyone checked the EGR valve for being open? If it is, it will create a massive vacuum leak and cause this issue.

The TPS voltage should be .5 to .75 volts at closed throttle. Are you sure the throttle plate is not partially open?

Roy

Thank you for your quick reply and willingness to help.
I don't know how to monitor system to give you the long term rim of the O2 sensor.
When I disconnect the IAC the idle does drop down to normal. The EGR valve opens and closes fine. I also checked the throttle plate and that is fully closed.

Okay, The IAC is fully retracted and making massive vacuum leak. Check the throttle body for carbon build-up.

If all is good, replace the ECM. That controls the IAC.

Roy

I cleaned the throttle body and got all the black Coke out. I will check it again to make sure it's not all blacked out again. When I clean the IAC it was moving up and down fine I will check that again. How much would a new ECM cost?

Rock auto has them for $136.00. The EM is a plug and play, no flashing required.

Roy

There was a little trail of blackish brown dry fluid in the opening from throttle body to the IAC. Must've been left from when I cleaned the throttle body, I cleaned IAC again. I drilled out the screw holes for the TPS and set it to .86 volts. I set it like that cause a few you and a few other others say set it to .75 volts and other's say .98 volts. So .86 is the mid way between the two. The car is quieter and runs a bit smoother but RPM'S still surged. Not as much or as high as before. Before I left work to drive home I checked the volts again. It jumped between .86 and .89 and settled at .89, not sure if it cause my multi-meter old and the probe ends have been soldered back on. I'll check it with my brother's Klien multi-meter. I set my base idle at 750 - 800 RPM'S but when I put it in drive/reverse it drops to 600 RPM'S, is that normal? Should I set base idle to 1000 RPM?
Thank you for all your help, I appreciate it so much. You're the greatest.

The base idle without the IAC hooked up should be 500 RPM. You have it set too high.

Adjust the base idle and let me know.

Roy

Okay, I'll adjust it on Friday and let you know.

Sounds like a plan.

Roy

It has been raining Friday and Saturday so I didn't set base idle but I did pull codes. 564 (fan control circuit failure) then a single flash and 332. Not sure if 332 is memory code. My engine fan motor is 2 months old and goes on to cool engine so I don't know why 564 code shows.
Last night my check engine light was on 3 minutes then off 3 minutes, over and over as I drove. Today it goes on 10 seconds then off 2-3 minutes, over and over. Second day little to no rpm surges though.

Let us deal with one issue at a time.

Adjust the base idle as I described and see if the one issue is resolved.

Roy

Okay. Do I adjust base idle with the stop screw or the idle bypass screw?

Stop screw on the throttle body.

Roy

Sorry Its been a while since my last reply. I've been experimenting with several TPS settings. I'm down to a setting of .72 and I still keep getting the surges. I've made two discoveries. #1)When the engine is cold and I pulled the IAC off the car stalls immediately. It stays running when the engine is warm and I pull off the IAC although kind of weak. #2)When the engine is cold I get a steady TPS reading of .72 but when the engine is warm I get an erratic bouncy reading between .72 and .73 on the voltmeter. Staying mostly towards .72, I'm using a good Klein tool multimeter. I'm not sure if my discoveries has any relevance to my problems but I thought I'd let you know. Also I did as you said and put the base idle at 500 RPMs with the IAC off

Here's a video of the reading bouncing erratically.

The TPS voltage is good. that is not causing the problem.

Can you upload a video of how it idles?

Roy

Sorry, it has been awhile since I wrote. I was experimenting. Before that I tried making videos a few times on how the car sounds when idles when warm and at start up, none of them sounded like the car in real life. I can tell you my brother and his friend that has a body shop said it sounds healthy and beefy. Both at idle and running down the road. I did make a few discovery and that is why I'm writing to seek your advice. I heard that not a 5 volt reading from the 5 volt vref wire on the TPS can cause surging. I tested mine and it reads 4.92 volts - 4.93 volts. I'm not sure what they said causes the low volt reading. A broken wire or a bad signal from where the wire comes from. My question is, would the low vref reading cause surging? If so how do I find the cause?
My sending a picture or 2 of Penelope the pretty purple pony your helping me with. She is actually more purple than it looks in the picture.

That voltage to the TPS is fine. You are good.

You need to look in another direction. The TPS is not the issue at all.

Roy

Where do you suggest I look?

This could be a vacuum leak in the engine, mass air flow sensor, PCV valve fuel injectors being dirty or fuel pressure.

Roy

I did a smoke test and no smoke leaked. I also covered the throttle body air intake port and engine stalled. I've cleaned the MAS about 6 or 7 times in the last year. The fuel pump, strainer and filter were replaced last summer, I'm guessing fuel pressure is good. I also put Lucas fuel injection treatment in every few months. The grommet for the PCV valve I've read is notorious for not fitting good. I've had the car 2 1/2 years and never changed the valve or grommet. How do I get to it?

Here's the videos of how it sounds running you asked for. The dashboard video is it starting up after sitting 9 hours in 60ish degree weather. The second video is after driving it 35 minutes home. The rattling noise in the engine is the alternator, its always been like that.

Do you have a scan tool that you can read what the IAC counts are?

Roy

No I don't. I have an ODB2 reader. I'll see if AutoZone has it.

Okay, keep me updated.

Roy

Hi Roy, I hope the new year is being good to you.
I did 2 smoke tests to checked for vacuum leaks and took off the air intake duct then covered the the front of the throttle body and the car stalled immediately. No vac leaks. Cleaned the MAS and ran codes, the only code is 574 (engine cooling fan fault). I can't find the PCV, it may have been eliminated when the hi-performance cool air induction set was installed. As for fuel pressure a new fuel pump, strainer and filter were installed about 8 months ago and the Schrader valve shoots a tall strong blast of gas. Should I buy a noid light and IAC test kit. Would that give the IAC count you asked for? I'm attaching a video of the car warm at idle & one of the car starting after a night sitting in the cold.

Okay, I attached the PCV location for you.

I would replace the IAC valve. It cannot be cleaned as the part that sticks is not available to clean.

The TPS has no effect on the high RPM. Make sure the voltage is set at .5 to .75 volts at closed throttle.

Roy

NOTE: The curb and fast idle speeds are controlled by the Power-train Control Module (PCM) and Idle Air Control (IAC) valve assembly. The IAC valve is not adjustable. A large increase or decrease in closed plate airflow from the calibrated level will not allow effective idle speed control.
The throttle body incorporates an orifice in the throttle plate controlling idle airflow as part of the sludge tolerant design.

Throttle Body Assembly Decal Location
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Throttle bodies with sludge tolerant design are identified with a yellow/black decal. This decal warns that the throttle plate stop screw must not be adjusted counterclockwise (backed off), as this will not reduce the engine speed but may cause the throttle plate to stick in the bore. Backing out the screw may be required if the throttle body has been previously serviced (a plug in the throttle plate orifice may be present), or the plate stop screw tampered with (TP Self-Test output out of range). The decal also warns that the throttle body must NOT be cleaned inside the bore, as this cleaning will impair the sensitive coating. The sludge accumulation will not affect the idle air flow. The cleaning procedure for the IAC valve still applies.

REMEMBER

A change in idle airflow can occur not only at the throttle body but other areas as well. You should enter the idle speed procedure only after other possible causes in the following areas are eliminated.
Contamination within the idle speed control device
Lack of fuel system control (excessively rich or lean)
Throttle sticking or binding
Engine not reaching operating temperature
Incorrect ignition timing
Incorrect or clogged PCV system
Vacuum leaks (intake manifold, vacuum hoses, vacuum reservoirs, power brake booster etc.

VERIFY

Transmission is in Park (A/T), or Neutral (M/T)
Parking brake is applied (automatic brake release disconnected where applicable)
Wheels blocked
Engine at operating temperature
Proper fuel pressure and no exhaust smoke
Correct and clean PCV system
Heater, A/C, and other accessories Off
Ignition timing is set to specification
EEC-IV diagnostics have been performed and vehicle malfunction indicated diagnostic trouble codes have been resolved.


PROCEDURE

STEP 1
With the engine Off, connect a tachometer according to manufacturers instructions. Disconnect the negative (-) terminal of the battery for 5 minutes, then reconnect it.

STEP 2
Start the engine and allow the idle to stabilize for two minutes. Goose the accelerator, and let the engine return to idle. Lightly depress and release the accelerator, then let the engine idle.

STEP 3
If the engine does not idle properly, proceed with this procedure.
NOTE: In some cases, even if the idle speed is OK, proceed with this procedure if the customer's complaint persists (idle air control duty cycle may be out of range).

STEP 4
Turn the engine Off, and install a 0.025 in feeler gauge between plate stop screw and the throttle lever.

STEP 5
Start engine and run at 2500 rpm for 30 seconds, then return to idle.

STEP 6
Place the transmission in Park (A/T), or Neutral (M/T).

Typical Throttle Return Screw Location
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STEP 7

Using a tachometer, verify idle speed is 704 +/-10 (A/T), or 640 +/-10 (M/T) rpm.
NOTE: Before proceding with this procedure, shut the engine Off, wait ten seconds. Re-start engine and recheck idle for two minutes. This eliminates the possibility of entering part throttle mode.

Throttle Plate Orifice Plug
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RPM TOO LOW

a. DO NOT clean the throttle body, check for the plate orifice plug.
IF NO PLUG, turn the screw clockwise to the desired rpm.

IF PLUG from previous service, remove and adjust the screw in either direction as required. Screw must be in contact with the lever pad after adjustment.

RPM TOO HIGH

a. Turn Off the engine.
b. Disconnect air cleaner hose.
c. Temporarily block the throttle plate orifice with tape. If the orifice already has a plug from previous service, proceed to Step (e).
d. Restart the engine, and check idle speed, using a tachometer.
NOTE: Vehicles with Mass Air Flow Sensors, reconnect the air intake duct hose before checking idle rpm. If the engine stalls, crack open the plate stop screw, DO NOT over adjust.
e. If rpm continues to be fast, Run Key On Engine Off (KOEO) Self-Test.
f. If rpm drops to the the value in Step 7 or lower, or the engine stalls, turn the engine Off, disconnect the air cleaner hose, and remove tape from throttle plate.
g. Install the proper color coded orifice plug, according to the throttle plate orifice size.
h. Reconnect the air cleaner hose, and Start the engine. Check the idle rpm using a tachometer. Turn the plate stop screw clockwise to the nominal rpm +/- 25 rpm shown in Step 7.

STEP 8
Shut the engine Off. Remove the feeler gauge between between the plate stop screw and throttle lever.

STEP 9
Start the engine, and allow the idle to stabilize for two minutes. Goose the accelerator, and let the engine return to idle. Lightly depress and release the accelerator, then let engine idle. If idle problem still exists, check for other possible causes.

STEP 10
Run the Key On Engine Off (KOEO) Self-Test for proper TP code output.

STEP 11
For Automatic Overdrive (AOD) transmission equipped vehicle, check and adjust (if necessary) the throttle valve pressure.

I just saw.this email you sent on January 12, 2020. It was in my spam box. I was checking the spam box before deleting them. Thanks for the diagram of PCV location. I'll check tomorrow.

You are welcome.

Always glad to help.

Roy

I attached a picture of where my PCV should be but its not there. I found it in a Hayne repair manual for my car. It should attach to a tube from the oil filler neck to the cold air induction near the throttle body. I've been running my car almost 3 years without one. The one that's made for my engine won't fit into the cold air induction tube a prior owner put on. I'm thinking of finding a PCV that will fit on even if I have to rig one up. What do you think?

What is the complete VIN number of your car?

VIN: 1FALP42T5SF105453.

You do not have the PCV in the passenger valve cover at the rear?

Roy

No PCV on passenger valve cover. Here's a video, am I not seeing it?

If they eliminated the PCV, that will damage the motor.

I would check the actual fuel pressure to be sure it is in spec.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Also, I am concerned the cat converter may be an issue as well. If it is partially clogged, it will cause surging.

https://www.2carpros.com/articles/how-to-test-a-catalytic-converter

Roy

I read a few days ago how not having a PCV or a bad one will damage and shorten the life engine. Since then I've been searching for it hard. That's why I bought one that will fit in the area it needs to be and fit in the tube in my engine. If I find for sure there is no PCV I'm going to see if I can find a stock air filter housing and duct work in a junk yard.

Correct.

That is something I would do.

The PCV will not cause the surging.

Can you check the actual fuel pressure? That will cause surging.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Roy

I'll go to AutoZone tomorrow and see if they have the test gauge.

Keep me updated.

Roy

Hi Roy. I hope you and your family are all doing well during this pandemic.I know it has been a while, I got frustrated and gave up trying to figure out what was wrong with the car. There was no PCV valve so I put one in where it should have went, the RPM's are still surging. I recently noticed that a digital OBD reader will not start the test in my car. But the OBD reader that you have to count the beeps on for the codes does work on my car. I'm thinking it's the ECU. What do you think?