title says it all, my mechanic said he thinks it's the computer, he can't get any error codes. I'm gonna verify that tomorrow when I bring the car home, but if that's the case, what am I looking at in terms of expense? What other things should I look at? I'm trying to decide if I should just try and sell the car as-is, cause it seems like something expensive breaks on it every couple of months...suggestions and advice welcomed!

 

The most likely cause is a leaking injector. Measure their resistance with an ohm meter when the engine is warm. If any of them are 12 ohms or less, its bad. They should be 15 ohms or more.
The cost of a new set of 22lbs 350 injectors is about $250.

 

A weak O2 sensor can also lead to a rich mixture without setting any trouble codes. Even less expensive to change out.

 

thanks, I'm assuming you mean parts only, yes? (no labor)

 

okay, I brought the car home and checked for codes myself...here's what I got:

14. High temperature indicated at engine coolant temp sensor

21. High voltage at throttle positon sensor

33. High voltage (low vacuum) at mass air flow sensor (or MAP sensor)

36. Burn off at mass air flow sensor OR Problem in transmission shift OR Fault in direct ignition system OR Missing pulses in electronic spark timing signal

43. Low voltage at electronic spark timing circuit

I dealt with #21 a couple of years ago, after another garage completely screwed that up. #14 makes sense cause the car had been running hot and went into the red once about a month ago (before the current problem arose). The other things, I'm not sure where to start or what to do.

Seemed odd that the mechanic said he couldn't get any codes...maybe he just didn't want to deal with it? He also said the car was running in "limp home" mode, whatever that is.

Aside from setting the tps correctly, any other suggestions? thanks in advance!

 

Nyb

1) Check sensor grounds - broken wires, loose wire lugs.
Code 14 - High temperature coolant temp sensor means that CTS is open or ground wire is disconnected and ECM see reference voltage (5.0Vdc). You can verify this by locating CTS - should be near thermostat housing. CTS will have a two pin connector - yellow and black. Get a cheap DVM, ign in key-off position, measure resistance between black wire and engine ground. Should be a very low resistance pass. If it open you found your problem. You can also check CTS by itself, with cold engine at about 22C measure resistance across CTS pins by itself - it should be around 2.6 to 2.7 kOhm.

Code 21 High voltage at throttle position sensor - check ground wire TPS and CTS use the same ground wire and lug.

Code 33 High voltage (low vacuum) at mass air flow sensor (or MAP sensor) -check ground wire..



//RF

 

Measuring from the tps's black wire to ground I get less than an ohm, so that appears to be OK. I also check from the black wire of what I believe to be the collant temp sensor to ground, also got less that 1 ohm.

When I check voltage betweem the tps's black wire and blue wire (terminals A and B) with the ignition on, I get between 4.2 and 4.6 volts, depending on how I move the tps around. In other words, moving the tps has some effect but I can't get anywhere near the recommended .54 volts. Does this mean that the tps has failed?

for future reference though, where would I begin to look for the ground lug? Both of those black wires disappear into a sheath with lots of other wires and I can't tell where they go.

thanks in advance...sure hope someone's online this weekend!

 

If the TPS shows 4.2-4.6 volts that means the ECM will think your at WOT all the time and flood the engine with gasoline causing a rich condition....

 

yes, that is what is happening. I was interested in why and what to do about it...

 

Disconnect tps connector. Measure TPS sensor resistance between A and C - it should be around 4.0 kOhm. If you get anything much larger time to replace TPS

//RF

 

carful better change that coolant temp sensor it cold be bad which tells the puter to give more fuel this happend to mine and fouled the plugs

 

True, with engine cold disconnect CTS plug and measure sensor resistance. With coolant temperature at about:
Temp(C) Resistance (Ohm)

20C (69F) measure CTS resistance - it should be 3.5kOhm.

As always, changing perfectly good sensors may accomplish very little.

I hope this helps - let us know

//RF

 

well if it aint just return it

 

it actually ranges from about 2K to 2.4K, depending on how I move the tps.
----------

RF quote:

>True, with engine cold disconnect CTS plug and measure sensor resistance. With coolant temperature at about:
Temp(C) Resistance (Ohm)
10 |-------| 5,728
15 |-------| 4,496
20 |-------| 3,555
25 |-------| 2,830
30 |-------| 2,268

20C (69F) measure CTS resistance - it should be 3.5kOhm. <


I can't get probes on the coolant temp sensor...it's just about inaccessible.

 

the sensor itself can be removed and tested in a pan of water if you like

 

Some version of TPS swapped pins around. But basicly inside they all look the same. Move DVM probes to different pin combination until you find fixed resistor. If you are only getting variable section then one of the legs is open.

For TPS a pig tail from JY works best or very small probes.

//RF

 

update: I determined that the tps was faulty, replaced it and set it to .54 volts. Also the PCV hose on that side was cracked and there was a huge vacuum leak into the throttle body, so I replaced that hose. Cleared the trouble codes, reconnected the battery and started the car. It started immediately and idled normally but would nearly stall when the throttle was opened. After it warmed up for about five minutes it got better. It hadn't run in about three weeks. I drove to the bank and then about seven miles on the highway to work, by that time it was running better than it has in a long time. I checked the trouble codes again and this time I got only two, 33 and 36.

the possibilities given for 36 are a little ambiguous but I'm guessing out of the choices it would probably be the one relating to the MAF sensor as I'm getting a 33 as well. I'll check the ground but any other ideas are welcomed.

I do remember that a few years ago when I had to reset the tps and clear the codes (after an incompetent garage set it incorrectly) that it seemed to take a day or two of driving the car before it really ran properly. Someone told me that it could take a few start/stop cycles for the computer to "reset" itself...any truth to this?

thanks again!

 

Disconnecting the power caused it to reset now it has to learn and tune itself to how you drive so be sure you drive it as you normal would and take it on a few freeway runs. It has 2 learning modes, short and long term.

 

cool! so does this mean that the 2 remaining trouble codes (33 and 36) will disappear after a couple of days?

 

If you've already cycled the ignition since you cleared the other codes then , no they won't go away.

 

If a burnoff signal is present at the MAF-sensor with the engine running , a code 33 will set. Be sure that the connection and the terminal at the burnoff relay are ok , and also check the maf-sensor connections... (code 36)... Maybe its time to buy a new burnoff-relay , cant be that expencive

 

thanks, how do I know which relay it is? I guess my question should be, is there a map of the relays available somewhere? thanks..

 

you have 3 relays , driverside next to the brake-booster...Fuelpump-relay (left) , Mafsensor-relay(middle) and Mafburnoff-relay (right)...But check partnumber to make sure...Hope this will help and that its not a faulty maf-sensor...

 

I changed the burnoff relay, still getting a 33 and a 36...if the MAF sensor relay is bad (as well as the MAF burnoff relay) would I still get these codes? Are both relays the same part number? The parts place I got it from only listed one relay in the category "MAF relay", in other words, they didn't seem to distinguish between "MAF sensor relay" and "MAF burnoff relay". I know the connections are different on the two relays, but the diagram was worn off the old relay and I couldn't read it. They're pretty cheap so I'll probably get another one on the way home so I'll have two new ones in there...I just want to know if they're the same, or if perhaps they sold me the wrong part (??)

 

Checked the partnumbers on the relays of my car (iroc-89)and it was the same , #14089936, so I assume it would be the same on your car...