Difficult to Diagnose Driveability problem

[djurs]

The TPS reads out 1.01 volts at idle and when revved (not sure how high, maybe 2000 RPM), it read 1.25 volts. I'm not sure how to test the IAC motor, I hear resistance testing is spotty, and I don't even know the values to look for. I touched an ohm meter to both prongs on the motor and got a 0.00 value, but I can't remember what scale I was using.

I cleaned the throttle body with throttle body and carb cleaner. I noticed of the two ports that go to the valve covers one had strong vacuum and the other none at all, I don't know the significance of this, but I'm curious if anyone knows the purpose of those ports.

I read codes out, both KOEO And KOER, both returned code 11 - System Ok.
I sprayed that throttle body cleaner on the vacuum lines in the engine compartment, but I think it was a waste since the engine did nothing but choke on the stuff while I was cleaning the throttle body, guess they do that to prevent engine damage due to too much highly flammable materials entering the engine. I hear brake cleaner works good for finding vacuum leaks... I haven't been able to find any any other way.

Any suggestions or ideas are helpful. I'm almost to the point of taking it to a shop, but I'm just worried no one there can find this problem without throwing parts at this thing.

 

[holyford86]

What is the problem exactly?

 

[djurs]

Yipes, I pasted this message in since my browser was having issues, and missed part of it.

While driving the vehicle revs 500-1000 RPM between shifts, and holds those revs for several seconds before slowly returning. Sometimes this problem happens, sometimes it doesn't. The vehicle also idles too high when warming up 1750, and sometimes idles too high anyway 1100 or so... Sometimes at a low speed coast it will start lurching, like it thinks it wants to go faster, and then changes it's mind.. almost as if I were tapping the throttle.

 

[djurs]

bump

 

[IMenriched]

Yipes, I pasted this message in since my browser was having issues, and missed part of it.

While driving the vehicle revs 500-1000 RPM between shifts, and holds those revs for several seconds before slowly returning. Sometimes this problem happens, sometimes it doesn't. The vehicle also idles too high when warming up 1750, and sometimes idles too high anyway 1100 or so... Sometimes at a low speed coast it will start lurching, like it thinks it wants to go faster, and then changes it's mind.. almost as if I were tapping the throttle.

Hey that OK...it happens.....BUT please more info....
what year? engine?? (presume 2.9) how many miles on the ticker?

start hard? bettter warm than cold?

how is the air filter? fuel filter? general maintence stuff.

the voltage on the idle seems abit high...thinking it should be down to .98 er so.

 

[djurs]

1989 2.9L 150,000 Miles, 2nd generation, one aftermarket head, one rebuilt head... Did have a block heater which I believe was obstructing the flow of coolant to the heater core, which I removed at the same time as this, the temperature was wildly erratic, replaced the thermostat as well... These symptoms are gone.

Not sure if I mentioned, the TPS is from NAPA, the IAC is borg warner that I got off the internet for really cheap $25.00.

Air filter is K&N and is fairly clean 5000 miles since last cleaning and oiling. Fuel filter on fuel rail seems to be a generic style that someone stuck in the fuel line and zip tied in place... I'm guessing they didn't like going after that pesky hard to reach thing in the frame. I have no idea how long it has been there, it's on my to do list to change the fuel filter out.

Starts every time. I've replaced the plugs with NGK platinums, I didn't touch the wires or distributor. I don't have a timing light or I'd time it, I wouldn't mind putting it to 11-12 BTDC since I live in colorado. The engine has a pretty severe lifter tap, which someone pointed out to me might be a wrist pin/king pin. The tap doesn't happen under load much, either accelerating or decelerating, but when holding a constant speed around 2300-3500 RPM.

Again the interesting thing here is that the symptoms are mostly gone since I cleaned the throttle plate and IAC and literally doused the intake manifold and ports with throttle body cleaner. When it was in full swing it seemed like the problem was less frequent when the engine was warmed before driving, and more frequent when I had to drive it before it was fully warmed.

I'm thinking it might be something that air is passing by when it's cold (contracted) and the engine is providing strong vacuum (4000 RPM).

Could I fix the TPS voltage by backing off the throttle screw near the intake manifold? I have done the fix suggested somewhere on here to attach zip ties to the throttle cable by the gas pedal to take up slack. Hopefully I don't have the throttle open any from that.

 

[IMenriched]

great info!
Could be the coolant temp sensor for the engine...yes there is 2 of them, 1 for the engine computer & 1 for the dash. if it tends to do better warm than cold....or the air temp sensor.

In which case I'm leaning towards the Air Temp Sensor, with all the carb cleaner that seems to be applied...and now improvement.
It is located midstream upper intake on the passanger side. If there was and maybe still is plenty of carbon in the upper intake...it maybe worth your time to remove and throughly de-carbon it ,as well as, the vacuum ports. Also check the back side of the throttle plate for carbon build up.

the fluctuating temp may have been due to the removeal of the block heater + the new thremostat...& developed a air pocket...that is now worked through.

Have you done a compression check?

 

[djurs]

I don't have a compression checker, and I don't know of any method to check without one.

I will remove and clean the ACT sensor as you suggested soon. Just replaced the fuel filter.

I don't know where the ECT sensor(s) are.

 

[Natedog]

.....I will remove and clean the ACT sensor as you suggested soon. Just replaced the fuel filter.

I don't know where the ECT sensor(s) are.

ECT is under the t-stat housing in the lower intake manifold....it is on the passenger side and slightly larger (and has two wires instead of one) than the gauge sensor which is on the driver's side lower manifold.

 

[djurs]

Recently installed new distributor cap and rotor, as well as a new ACT sensor, and while it's minor a better hose for the "hot air intake blend door thingie," Next on agenda is ECT sensor... I haven't had any issues with the new changes, but then again I haven't driven it much either. We'll see.

 

[IMenriched]

Sounds like you're getting the issues run down...thats great.

winter weather is tough to get things to run well...always wonder if it is because of the cold...or whether you really got problems...& as to what is affecting what.

how is the the tick/knock now that it is running better?