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Location:
Brisbane, Queensland
Registered:
April 2003
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Odd misfiring problem
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Wed, 03 March 2004 02:13
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Car in question is an australian delivered sprinter which has had the jap spec RWD TVIS 86kw 4AGE dropped in. Otherwise basically standard. Recently out of the blue it has started acting very strangely. It is a little hesitant to start but once it has it idles perfectly and up to about 10% of throttle travel it is perfectly fine and dandy. Beyond 10% throttle it dies and misfires/backfires/stutters/coughs like nobodies business... drop back down to very little throttle and its fine.
Beyond about 6000rpm it runs fine at all throttle positions, my thought is the idle switch component of the TPS is rooted and is permanently showing that it is at idle.
I removed the TPS and cleaned it as best as possible with contact cleaner but it made no difference. I have the instructions on how to backtest the TPS and will be doing it shortly and will report back.
Has anyone had any similar problems and found a solution?
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Location:
Brisbane, Queensland
Registered:
April 2003
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Re: Odd misfiring problem
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Wed, 03 March 2004 05:32
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Tested the TPS, all numbers came back in the expected ranges. When I started playing with the map sensor, bumping it seemed to affect the idle speed but I couldn't manipulate it in any way that resolved the problem. I removed the housing portion of the plug the the map sensor so I could plug the pins directly into the female plug in the loom and test it there, all figures came back as would be expected, although I didn't have a vacuum gauge to give specific comparisons.
Reassembled to the plug and reattached the map sensor its mount, tried driving it with the map sensor vacuum line disconnected, was much better, still had a bit of a stutter but was nowhere near as bad.
Reconnected the map sensor, was as bad as it has ever been...
RE-DIS-connected the map sensor and it seemed to make a slight difference but not as good as the previous disconnection...
All signs point to the map sensor, but it isn't conclusive. Distributor cap and rotor button are new and in good condition. The ref and sync triggers appear to be in good working order.
Anyone in brisbane got a map sensor I could swap with for 5 minutes to eliminate it?
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Location:
Brisbane, Queensland
Registered:
April 2003
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Re: Odd misfiring problem
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Wed, 03 March 2004 09:46
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In playing with it, something I was doing seemed to be affecting the severity of the problem, unfortunately I couldn't pin what. Whether it was the jostling of the map sensor itself or the moving of the wires. The severity seems to come and go, I'm about to head out and try testing the sensor outputs at the ECU instead of at the sensors themselves to identify if it is a wiring problem.
A few other threads described VERY similar problems but nobody posted how they solved the problem. Anyone?
I'm now chasing anyone in brisbane with known working parts, either on their car or as spares to test.
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Location:
Sydney
Registered:
January 2004
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Re: Odd misfiring problem
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Wed, 03 March 2004 09:57
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maybe silly but how old is the fuel filter? Something I read said that a clogged fuel filter can allow the car to idle properly but once under throttle the extra fuel required cannot be met through the extra restriction. Might be worth replacing..cheap and hopefully easy to fit (mine was about 15 bucks through wholesale supplier).. I'm having trouble fitting my new one cause the inlet fitting is butchered!
Good luck
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Location:
Brisbane, Queensland
Registered:
April 2003
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Re: Odd misfiring problem
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Wed, 03 March 2004 10:17
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I might replace it tomorrow just to be on the very safe side but then you'd expect it to struggle high in the rev range and as I mentioned, above about 5500-6000rpm it clears up and works fine across the whole throttle range.
I suspect the answer is in that behaviour. My guess is that at that point the computer starts to operate without using the input from the TPS *or* from the MAP sensor.
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Location:
NSW
Registered:
September 2003
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Location:
NSW
Registered:
September 2003
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Re: Odd misfiring problem
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Wed, 03 March 2004 10:35
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Hang on... I'm having a conversation with myself here... (as usual) but 86KW + MAP...?????
Weren't only the 100kw GE's MAP Sensed?
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Location:
Brisbane, Queensland
Registered:
April 2003
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Re: Odd misfiring problem
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Wed, 03 March 2004 10:55
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Definitely map sensor equipped... Mind you, it still just means the load sensor is out, so I'm fairly hopeful it'll be the map sensor, or less ideally the wiring between the map sensor and the ECU.
Still chasing someone in brisbane who I can temporarily swap some parts with to troubleshoot. 6 pack of bundy and cola guaranteed and mebbe some more if the problem is sorted.
Failing that, I might be chasing a map sensor to suit, anyone got one for sale?
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Location:
NSW, East Coast
Registered:
July 2003
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Re: Odd misfiring problem
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Wed, 03 March 2004 23:31
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Check for air leaks first, just spray some carby cleaner around the inlet manifold, the engine note will change if you have a leak.
Double check your timing, put computer in diagnosis mode first.
Should be 10 deg btdc,
Also check you coolant level.
If in doubt i have a map sensor.
I had a very similar problem about 7mths ago, turned out to be tps was misaligned and the timing advance was out a little?
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Location:
Brisbane, Queensland
Registered:
April 2003
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 Re: Odd misfiring problem
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Fri, 05 March 2004 02:16
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Tried another MAP sensor this morning, made no difference. The problem slightly improves with the map sensor vacuum line disconnected.
Had a bit of a look at the wiring loom, seems the conversion was a bit of a hatchet job (this is my mates car, not mine). There is no diagnostic connector where it should be and I can't find any connector matching what I'm lookign for, I take it that it is grey like other toyota diagnostic connectors?
Wiggling the loom itself near the computer seemed on a few occaisions to make the idle jump around but now that effect seems to have disappeared, so I suspect I've either reconected previously dubious connections to the main ECU plugs, or permanently severed them, no difference in the running of the car still though.
I'm starting to get to the end of my rope now, I'm still plodding through it though, I think I'll start tracing the location of where the diagnostic plug should be by following the loom or failing that, just make the connection at the ECU instead.
Which brings me to my next problem... check engine light? what check engine light, the oil light doesn't work (although the guage does) and there is no seperate check engine light I can see anywhere on the australian spec dash. Can someone give me a location description of where it is.
Failing that, I guess I can make a check engine light from the ECU as well. If anyone has any suggestions or questions, any help would be greatly appreaciated, I was hoping to have this car running again by today so my friend could use it over the weekend for house hunting.
I'm more than willing to supply details/digital photos of any items that people have questions about. In short, I'm *VERY* open to any input.
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Location:
Brisbane, Queensland
Registered:
April 2003
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Re: Odd misfiring problem
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Fri, 05 March 2004 02:24
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Oh, and in reply to earlier questions. No air leaks. Can't put the computer into diagnostic mode... yet.
Coolant level is fine, had to refill it when I removed the map sensor as I had to remove the whole throttle body as someone before me had mauled the screws retaining the sensor. Nice pretty stainless allen headed items have gone in as replacements.
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Location:
Brisbane, Queensland
Registered:
April 2003
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Re: Odd misfiring problem
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Fri, 05 March 2004 02:30
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Just another quick question... The efi service connector labelled in the centre of this picture, I take it this is likely to represent one of the two pins in the instructions for putting the ECU into diagnostics mode? Anyone know what the other pin is? is it a power feed or just an earth or something more sinister?
By the same token, the check engine connector at the bottom of the picture, can anyone confirm that it is the power output (or switched earth) for the check engine light? I'll go have a play very shortly with the multimeter but its understandably easier to get the knowledge from someone else.
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Location:
Brisbane, Queensland
Registered:
April 2003
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Re: Odd misfiring problem
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Fri, 05 March 2004 09:58
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Well, it looks like I may have found the problem. Ran through a few other things and went to testing the sensor readings at the ECU instead of at sensors themselves. Started with the map sensor which I had pinned as the culprit and it tested up fine, then went on to the TPS which also tested up fine. Then tried taking the readings for the TPS (which are resistances) while the engine was running, the TPS tests fine under no load but the resistance goes infinite at a point which corresponds to the start of the misfire problem when connected to power.
Tried the local wrecker to track a replacement TPS but struck out, might have sourced one interstate but I'll try other wreckers tomorrow to save on shipping time and cost.
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Location:
Brisbane, Queensland
Registered:
April 2003
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Re: Odd misfiring problem
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Sat, 06 March 2004 09:03
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Tried a new TPS, no difference. Tried disconnecting the vacuum feed to the FPR in case it had some unusual fault, no difference. Tried crying into my hands, no difference.
Anyone care to offer any random guesses?
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Location:
Brisbane, Queensland
Registered:
April 2003
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Location:
Brisbane, Queensland
Registered:
April 2003
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Re: Odd misfiring problem
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Sun, 07 March 2004 08:52
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Okay.. Another update.
Followed the testing regime outlined in the FSM under 'testing with a voltmeter/ohmeter', barring the fact that the STA signal wire is not connected every voltage tested up A-OK. Including for the TPS, which is interesting as its the resistance across VTA and E2 goes crazy when the engine is running, which means the variation in the resistance readings is obviously in the ECU not the sensor, whether this is significant or just normal I really don't know.
I'm starting to strongly suspect the ECU... so once again, I'm hunting for anyone *anywhere* in SEQ with an 86kw 4AGE MAP sensor equipped car with the stock computer.
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