2.9 High Idle and Revs

Notice lately that when I shift gear the engine wants to rev up to about 3K and then fall back down. The idle is also running around 1200, and it used to be right at about 900. Also when stopping the idle doesn't drop until the truck stops.

Does the sensor on the tranny control the idle any? Or is this likely a TPS or IAC issue?

I got to work this morning and went to leave about 20 minutes later and the truck wouldn't start. Just cranked and cranked. Waited about 2 hours and it cranked, hiccuped and then started. SHut it off, started right back up.

I am thinking FPR, Cracked Dist Cap ( that can't be it because yesterday it wasn't raining and it didn't want to start either) leaky injector, or the TFI... what are the symptoms of that?

The problems are extremely general, I am pretty stumped.

Sometimes a bad TFI will cause the truck to stall while it's running and not start back up until it cools off again.

The only thing I can think of is to check for spark when it doesn't decide to run again. That way you can identify if it's a fuel or spark problem. If neighter, then it's an electrical problem. Or even take some starting fluid and a flat head and see if it fires off that the next time it dies.

IAC will cause some REALLY odd issues. My friend's 5.0L howled and revved contantly 2.5K RPM, ran hotter than normal when his IAC went. Does the idle change with in unhooked? If not, then it's either bad, or it's wiring.

Have you checked for vacuum leaks (particular between the upper and lower intakes and vacuum lines), and have you tried to pull codes?

I couldn't see one leaky injector preventing the engine from starting entirely. Your fuel pressure would drop pretty quickly if this were happening.

Test the voltage on the TPS with an analog volt meter, but you can get a general idea if it working properly with a digital if that's all you have. I remember the ground being pretty easy to identify, you have a 5v+ reference voltage constant, and the other is a 0-5v range that's pretty much a variable resister. It should be .98 idle - ~4.5/5.0v+ and should sweep (with the analog) the needle smoothly on the meter.

Pete

I unplugged the IAC and the truck shut off... Was it supposed too. Didn't sputter, just died. Checked all I could to see if anything was loose. It idles at like 1200rpm.

I checked the timing and it is on 10d TDC, I pulled the codes.

KOEO I got 11.
KOER I got 21.

Would a 21 code cause my problems?

was the engine warm when you pulled the KOER codes?

You're IAC seems to be functioning, usually mine will rev up and down, then die but, a bad ECT could be causing the engine to run too rich or too lean.

I briefly looked in my Chilton's, EVTM, and How to rebuild 60 degree engines and could not find a temperature vs. resistance chart for the 2.9L.

I did find this, (for 92 3.0L)

http://z.about.com/d/autorepair/1/0/I/A/41928895.gif

maybe some one could chime in if it's not accurate? It would be good to add some of this stuff to the technical library. I am half tempted to go outside and verify it, but it's just too damn cold and I have an upper respiratory infection.

Pete

Well I couldn't imagine it causing the problem so I couldn't leave well enough alone. I went out and unplugged the ECT sensor. Truck wouldn't start.. acted JUST LIKE it did this morning. So I plugged it back in, yay, it started after cranking for a minute.

Unplugged it again, no start... Plugged it back in and left the plug loose so I could take it off once the engine was running.

Started it and pulled the plug out of the ECT. The idle immediatly jumped. So I got in and revved it to get the idle to drop and ill be damned if it didn't rev and hang there just like it did when I would shift. So I think I found the problem.

The exhaust smelled extremely rich. I think the sensor is telling the truck it's extremely cold and flooding it out.

Any thoughts?

This sensor is less than a year old. WTF

holyford86 said:

was the engine warm when you pulled the KOER codes?

Click to expand...

Yeah, my mechanical guage said 180.

test your ect sensor

So do I pull it out to test it or leave it in the truck?

For $13 bucks I minds well replace it. Unless it's the wiring.. or not the problem.

But I tested it every which way but up. Just odd that the problem is innermitent.

But could this bad sensor flood the motor enough to make it not start?

Jspafford said:

So do I pull it out to test it or leave it in the truck?

Click to expand...

Leave it in the truck. From the looks of the diagram - it looks like you test it like the TPS. Get the engine up to temp, then find the ground and test the signal wire to the PCM, the other should be a 5v+ ref constant.

Jspafford said:

But could this bad sensor flood the motor enough to make it not start?

Click to expand...

Don't know, never had one go bad on me before. I replaced my old one when I rebuilt my 2.9L 4 years ago.

Pete

Edit:

Jspafford said:

This sensor is less than a year old. WTF

Click to expand...

It happens sometimes.... Best bet is to test it to be sure.

Pete

what's the ECT

Common Engine Terms:

FPR - fuel pressure regulator
MAP - manifold absolute pressure (sensor)
MAF - mass air flow (sensor)
TPS - throttle position sensor
TFI - Thick Film INTEGRATED (not Ignition)
HEGO or O2 - (heated exhaust gas) oxygen (sensor)
ACT - air charge temperature (sensor)
CTS - coolant temperature sensor
EGR - exhaust gas recirculation (valve)
IAC - Idle air control (bypass valve)
CANP - (charcoal) cannister purge (valve)
EEC - evaporative emission control (charcoal cannister and related components)
PCM - powertrain control module (computer)
CEL - check engine light (old)
MIL - malfunction indicator lamp (modern -- not all malfunctions are in the engine)
DTC - diagnostic test code
KOEO - key on/engine off
KOER - key on/engine running
SPOUT - spark output (a wire that can be disabled by removing a connector on TFI-IV equipped engines)
FRP - Fuel Rail Pressure Sensor
FTP - Fuel Tank Pressure
EVMV - Electronic Vapor Management Valve (modern version of the CANP)
VSS - Vehicle Speed Sensor
GEM - Generic Electronic Module
FMEM - Failure Mode Effects Management
KAM - Keep Alive Memory
EFI - Electronic Fuel Injection
CFI - Central Fuel Injection
SEFI - Sequential Electronic Fuel Injection
EGR - Exhaust Gas Recirculation
EVR - Electronic Vacuum Regulator (regulates vacuum to the EGR)
EVP - EGR Valve Position
DPFE - Delta Pressure Feeback EGR
TBI - throttle body injection
ECU / ECM - engine control unit / module
VSS - vehicle speed sensor
MSDS - material safety data sheet
EMA = engine manufacturers association
VI - viscosity index
ABS - antilock brake system
AFR - air fuel ratio
TDC / BDC - top / bottom dead center
DIS - distributorless ignition system
EEC - evaporative emission control
EGO sensor - Exhaust gas oxygen sensor
MPFI - multi point fuel injection

Psychopete said:

You're IAC seems to be functioning, usually mine will rev up and down, then die but, a bad ECT could be causing the engine to run too rich or too lean.

I briefly looked in my Chilton's, EVTM, and How to rebuild 60 degree engines and could not find a temperature vs. resistance chart for the 2.9L.

I did find this, (for 92 3.0L)

http://z.about.com/d/autorepair/1/0/I/A/41928895.gif

maybe some one could chime in if it's not accurate? It would be good to add some of this stuff to the technical library. I am half tempted to go outside and verify it, but it's just too damn cold and I have an upper respiratory infection.

Pete

Click to expand...

you said, "Sometimes a bad TFI will cause the truck to stall while it's running and not start back up until it cools off again." how does the TFI do that??

are you sure you don't mean the ECU / ECM - engine control unit / module, instead...

Common Engine Terms:

FPR - fuel pressure regulator
MAP - manifold absolute pressure (sensor)
MAF - mass air flow (sensor)
TPS - throttle position sensor
TFI - Thick Film INTEGRATED (not Ignition)
HEGO or O2 - (heated exhaust gas) oxygen (sensor)
ACT - air charge temperature (sensor)
CTS - coolant temperature sensor
EGR - exhaust gas recirculation (valve)
IAC - Idle air control (bypass valve)
CANP - (charcoal) cannister purge (valve)
EEC - evaporative emission control (charcoal cannister and related components)
PCM - powertrain control module (computer)
CEL - check engine light (old)
MIL - malfunction indicator lamp (modern -- not all malfunctions are in the engine)
DTC - diagnostic test code
KOEO - key on/engine off
KOER - key on/engine running
SPOUT - spark output (a wire that can be disabled by removing a connector on TFI-IV equipped engines)
FRP - Fuel Rail Pressure Sensor
FTP - Fuel Tank Pressure
EVMV - Electronic Vapor Management Valve (modern version of the CANP)
VSS - Vehicle Speed Sensor
GEM - Generic Electronic Module
FMEM - Failure Mode Effects Management
KAM - Keep Alive Memory
EFI - Electronic Fuel Injection
CFI - Central Fuel Injection
SEFI - Sequential Electronic Fuel Injection
EGR - Exhaust Gas Recirculation
EVR - Electronic Vacuum Regulator (regulates vacuum to the EGR)
EVP - EGR Valve Position
DPFE - Delta Pressure Feeback EGR
TBI - throttle body injection
ECU / ECM - engine control unit / module
VSS - vehicle speed sensor
MSDS - material safety data sheet
EMA = engine manufacturers association
VI - viscosity index
ABS - antilock brake system
AFR - air fuel ratio
TDC / BDC - top / bottom dead center
DIS - distributorless ignition system
EEC - evaporative emission control
EGO sensor - Exhaust gas oxygen sensor
MPFI - multi point fuel injection

Psychopete said:

The problems are extremely general, I am pretty stumped.

Sometimes a bad TFI will cause the truck to stall while it's running and not start back up until it cools off again.

The only thing I can think of is to check for spark when it doesn't decide to run again. That way you can identify if it's a fuel or spark problem. If neighter, then it's an electrical problem. Or even take some starting fluid and a flat head and see if it fires off that the next time it dies.

IAC will cause some REALLY odd issues. My friend's 5.0L howled and revved contantly 2.5K RPM, ran hotter than normal when his IAC went. Does the idle change with in unhooked? If not, then it's either bad, or it's wiring.

Have you checked for vacuum leaks (particular between the upper and lower intakes and vacuum lines), and have you tried to pull codes?

I couldn't see one leaky injector preventing the engine from starting entirely. Your fuel pressure would drop pretty quickly if this were happening.

Test the voltage on the TPS with an analog volt meter, but you can get a general idea if it working properly with a digital if that's all you have. I remember the ground being pretty easy to identify, you have a 5v+ reference voltage constant, and the other is a 0-5v range that's pretty much a variable resister. It should be .98 idle - ~4.5/5.0v+ and should sweep (with the analog) the needle smoothly on the meter.

Pete

Click to expand...

I've seen you post this list of acronyms in about 5 posts now...

ECT is engine coolant temp sensor.
I don't know of anyone who calls them a CTS.

The TFI module is on the distributor, it has NOTHING to do with the ECM

I changed out the sensor. Oddly enough the one I took out was ALL black plastic. The connector, the threads, the tip... The one I put in was grey plastic on the connector and the threads and tip were copper.

Seemed like a much nicer piece.

Fired the truck in 10 degree temps and it fired right up and idled at 850rpm for a second and then went into the warm up RPM. Then after a few minutes and it started to warm up it dropped back down to normal idle speed.

Seems to have fixed the problems. I didn't have a volt meter worth a damn, so I just replaced it..

I was beginning to wonder why my mileage had been steadily dropping. I think the sensor was running the motor too rich.