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Question on SPFI pinging problem


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27 replies to this topic

#1 edrach

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Posted 19 June 2005 - 09:46 PM

Starkiller was over here today and we tried to make some headway on his car's pinging problem. Car is an '89 SPFI wagon with manual tranny if that helps any. The obvious things such as timing and advance have been checked and are as they belong. He's running hi-test and it pings and gives a code 32 for the O2 sensor. I put my DVM on the output of the existing O2 sensor and I got a very low reading...around 10 mvdc. I unplugged that O2 sensor and plugged in another (used O2 sensor) without installing it in the cat and got a reading of 375 mv. I installed the second O2 sensor into the cat and got a reading of about 75 to 80 mv. I noticed that the original O2 sensor was quite white (too lean I thought) and pulled the number one sparkplug and it too indicated a very lean burn. After re-installing the #1 sparkplug, I unplugged the MAF and noticed no change in the reading of the O2 sensor or of the idle. Now I think I may have a bad MAF making the ECU think there's too little air and causing the lean condition, or whatever controls the mixture is ignoring the O2 sensor reading, and lastly maybe a restricted port in the throttle body. Qman suggested that maybe the temp sender is giving a false reading to the ECU of engine temp; temp guage was at a 1/4 for a partially warmed up engine and the sender measured 62 ohms. Any other thoughts or other suggestions out there?

#2 hooziewhatsit

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Posted 20 June 2005 - 12:14 AM

what does the ground look like for the O2 sensor? (resistance from negative cable un-hooked to exhaust)

A bad ground there could account for the funky O2 reading un-installed vs. installed.

Oh yea, when you measured the O2 voltage with it not in the exhaust, what did you do for the ground then?

#3 edrach

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Posted 20 June 2005 - 12:37 AM

Used the body of the O2 sensor; this sensor is only a single wire; gets it's ground from the body of the cat. Funky reading uninstalled is really a better reading. From what I read on another thread, O2 sensor should read between 500 and 700 mv.

what does the ground look like for the O2 sensor? (resistance from negative cable un-hooked to exhaust)

A bad ground there could account for the funky O2 reading un-installed vs. installed.

Oh yea, when you measured the O2 voltage with it not in the exhaust, what did you do for the ground then?



#4 NorthWet

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Posted 20 June 2005 - 12:43 AM

I wouldn't have expected any voltage if the non-installed EGO sensor was not up to temperature... though there was a discussion last fall/winter about the ECU putting a 5volt health-monitor signal onto the EGO sensor's line. I have a MAF that I can loan Alan. Did you only look at one sparkplug? I would expect that the SPFI would use a separate coolant temperature sensor (as does the MPFI), rather than use the temp guage sender.

TPS might be misreporting. From what I hear, pretty common for SPFI, and correctable by adjusting TPS position.

When does the pinging occur? WOT, partial throttle, high-/low-/mid-rpm? Does it sound like all cylinders or just one? What is the oil consumption like, and do any of the plugs show oil?

With EGO sensor disconnected, the system should go open-loop and default to a mixture that is richer than optimum. If it is still too lean, then there is probably a vacuum leak, a sensor misreporting/malfunctioning, or insufficient fuel flow through the injector.

Anybody have a clue about how the SPFI injector functions? Is it constant injection, with the flow rate modulated, or is it pulsed like the MPFI?

#5 archemitis

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Posted 20 June 2005 - 12:45 AM

the o2 sensor will never make you ping.
the main thing these cars look at is the maf. if its a bad maf, you will have a car that doesnt run well.

if you have a bad o2 sensor... well, not much happens. i dont run one on my xt6. and morganm is not currently sporting one either.
im not saying that its cool to run around with no o2 sensor, but id look elsewhere for any problems with pinging.

carbon in the cylinders, would be another thing to check, if the maf is good. or the water temp sensor for the computer.

#6 edrach

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Posted 20 June 2005 - 12:53 AM

I only looked at one sparkplug and original O2 sensor...they were both quite white (too lazy to check the other three plugs). I saw no trace of oil on the #1 'plug. Starkiller can tell you when the pinging occurs (I haven't driven his car) but I suspect it is all the time. I believe starkiller has driven the car with the O2 sensor disconnected and I think it still pings then. I didn't look for another temp sensor; the one I found was on the intake manifold just above the #1 cylinder. What is proper way to adjust TPS?

I wouldn't have expected any voltage if the non-installed EGO sensor was not up to temperature... though there was a discussion last fall/winter about the ECU putting a 5volt health-monitor signal onto the EGO sensor's line. I have a MAF that I can loan Alan. Did you only look at one sparkplug? I would expect that the SPFI would use a separate coolant temperature sensor (as does the MPFI), rather than use the temp guage sender.

TPS might be misreporting. From what I hear, pretty common for SPFI, and correctable by adjusting TPS position.

When does the pinging occur? WOT, partial throttle, high-/low-/mid-rpm? Does it sound like all cylinders or just one? What is the oil consumption like, and do any of the plugs show oil?

With EGO sensor disconnected, the system should go open-loop and default to a mixture that is richer than optimum. If it is still too lean, then there is probably a vacuum leak, a sensor misreporting/malfunctioning, or insufficient fuel flow through the injector.

Anybody have a clue about how the SPFI injector functions? Is it constant injection, with the flow rate modulated, or is it pulsed like the MPFI?



#7 starkiller

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Posted 20 June 2005 - 01:01 AM

pinging occurs really all the time, but worse under load, going uphill...any gear...oil consumption is ok...cant tell if the pinging is all cylinders as my ears are what they used to be(darn rock'n'roll) :D


was going to look for another maf and temp sensor tomorrow at the pap before worrying about another throttle body...

#8 edrach

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Posted 20 June 2005 - 01:09 AM

if the maf is good. or the water temp sensor for the computer.

If there's a separate water temp sensor for the computer, where is it? I was surprised to see the engine continue to run at idle when we unplugged the MAF; makes me think the MAF is bad.

#9 Phaedras

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Posted 20 June 2005 - 02:22 AM

I'm having big pinging issues as well, especially under load. Idle issues as well. Barring the IAC and assuming the MAF, how do you check it?

#10 starkiller

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Posted 20 June 2005 - 09:43 PM

bumpo

#11 archemitis

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Posted 20 June 2005 - 10:14 PM

bumpo


whats the bump for?
its in your hands now, swap maf, see what happens. run some seafoam in the gas and engine, see what happens.
swap water temp sensor...

rage it!

#12 starkiller

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Posted 20 June 2005 - 11:04 PM

swapped out temp sensor, will see what happens tomorrow..have already run seafoam in gas tank....will see if tacoma pap has the maf tomorrow...

#13 cmiller

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Posted 20 June 2005 - 11:15 PM

My '92 Loyale has around 165,000 on is and was pinging under load. I started to use supreme gas and that solved the pinging problem. (expensive though) :(

#14 starkiller

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Posted 20 June 2005 - 11:17 PM

tell me about it...2.53 gal...use shell/chevron/texaco...still pings..hoping the temp sensor does it or a new maf :(

#15 NorthWet

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Posted 21 June 2005 - 12:18 AM

I doubt that the temp sensor is the culprit. If it is misreporting the temp as too low, the mixture should be richer than required. If it is reporting too high, well, it is either a) so high that the ECU recognizes it as a false reading, B) so high that the ECU enriches the mixture to try to mitigate detonation, or c) the ECU does not know what to do with the reading so does nothing extraordinary.

My money would be on something else, something underreporting airflow (MAF) or engine load (TPS?), something misinterpreting the sensor data (ECU), or something mistranslating the ECU's instructions (TBI). Or a vacuum leak.

I have spares if you need them.

#16 edrach

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Posted 21 June 2005 - 12:28 AM

I keep telling you to get gas at the Shell or 76 just down the road from my house; currently high test is $2.40/gal.

tell me about it...2.53 gal...use shell/chevron/texaco...still pings..hoping the temp sensor does it or a new maf :(



#17 edrach

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Posted 21 June 2005 - 12:30 AM

Based on what I think I saw yesterday I'm thinking bad MAF or an injector that won't open up. Again, how can I check that the TPS is correct?

I doubt that the temp sensor is the culprit. If it is misreporting the temp as too low, the mixture should be richer than required. If it is reporting too high, well, it is either a) so high that the ECU recognizes it as a false reading, B) so high that the ECU enriches the mixture to try to mitigate detonation, or c) the ECU does not know what to do with the reading so does nothing extraordinary.

My money would be on something else, something underreporting airflow (MAF) or engine load (TPS?), something misinterpreting the sensor data (ECU), or something mistranslating the ECU's instructions (TBI). Or a vacuum leak.

I have spares if you need them.



#18 subynut

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Posted 21 June 2005 - 12:44 AM

This is an intristing thread. I have a similar problem in that she runs lean to the point of fuel starvation till about 4500rpm when she finally goes rich and she takes off. Just tried that maf trick and my Suby's rpm came up by maybe 200rpm when I unplugged it. Very intristing........

#19 hooziewhatsit

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Posted 21 June 2005 - 01:02 AM

Based on what I think I saw yesterday I'm thinking bad MAF or an injector that won't open up. Again, how can I check that the TPS is correct?


http://www.ultimates...position sensor

a couple posts down Garner posts a link to the FSM outlining how to test the TPS

#20 Ross

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Posted 21 June 2005 - 01:35 AM

Unplug the MAF, and go for a drive. Without the MAF, the computer should run too rich and wont detonate.
If that fixes it, i would say it is a bad MAF.

IF it still pings without the MAF connected, i would suspect an injector problem maybe?? Carbon build up???

#21 NorthWet

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Posted 21 June 2005 - 01:39 AM

Thanks. I had spent half an hour searching for TPS info, but had no luck.

I do not think that it is the injector not opening up, as starkiller says that the pinging is across the range, not just at high-fuel-flow. So if it is the injector, it is never really flowing the right amount of fuel.

#22 hooziewhatsit

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Posted 21 June 2005 - 01:42 AM

Unplug the MAF, and go for a drive. Without the MAF, the computer should run too rich and wont detonate.
If that fixes it, i would say it is a bad MAF.

IF it still pings without the MAF connected, i would suspect an injector problem maybe?? Carbon build up???


IIRC, shouldn't the car not run very long with the MAF unplugged? after a similar thread a while ago I went out and unplugged mine. It would run for a few seconds then die.

wouldn't this pretty much point to a problem with the MAF?

#23 Ross

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Posted 21 June 2005 - 01:48 AM

Would the TPS have such a dramatic effect to cause this detonation?

Does the injector use a coil to open? If its had too much curent flow or something the coil could be partially burned out, opening it less for a given input voltage??

Got the right spark plugs in there??:rolleyes:

Just thinking about it, a lean mixture shouldn't cause detonation at low throttle. The computer will already have it running on excess air under low throttle.

#24 Ross

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Posted 21 June 2005 - 01:50 AM

IIRC, shouldn't the car not run very long with the MAF unplugged? after a similar thread a while ago I went out and unplugged mine. It would run for a few seconds then die.

wouldn't this pretty much point to a problem with the MAF?


Well, theoretically the computer should go into "limp" mode so that the car is driveable. Should increase the idle slightly and increase the rate of fuel going in according to rpm and tps only - it will run quite rich at low throttle, but may lean out under full load, i dunno.

My ea81t (VAF not MAF) runs ok without vaf connected - slow and crap but it doesn't detonate and you can drive it ok.

#25 NorthWet

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Posted 21 June 2005 - 01:11 PM

Would the TPS have such a dramatic effect to cause this detonation?

Does the injector use a coil to open? If its had too much curent flow or something the coil could be partially burned out, opening it less for a given input voltage??

Got the right spark plugs in there??:rolleyes:

Just thinking about it, a lean mixture shouldn't cause detonation at low throttle. The computer will already have it running on excess air under low throttle.

If the TPS is underreporting the throttle opening, the ECU could think that the engine is not under as much load as it really is. The spark plugs should be right; he is almost certainly running NGKs which have a wider heat range to begin with, plus this doesn't seem to be load dependent.

Part throttle is not a guarantee of a normally lean mixture, and neither is low engine speed. Depends too much on how the ECU was programmed.




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