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I would insert my 2 cents about what came to mind:
1) failed neutral safety switch – does the car cranks on Neutral gear?
2) Immobilizer – could be locked up?Returned from a long drive, and tested with engine off as requested:
With engine off MAP is reading 27.8 inHg. (you were on spot :))
LTFT = – 8.6Idk if this tool has an option to give me such reading. (should be done via multimeter?)
by the way, I’m about 650m above sea level.. heard it could affect the map readings.It was closest to 0 LTFT at 2k rpm, when my map was soaked in dirt. ( -0.8 ) [ fluctating STFT = -5.5 , -10.2]
afterwards best value was again at 2k rpm (3.9) [ fluctating STFT = -3.9 , -10.9]Didn’t performed yet the water test.
As far as I see, this model lacks MAF, no supported sensor feedback.
Nor I could find it physically.Updated info after driving around for about an hour today:
If vacuum leak, suspected areas:
Loose
later on i’ll water spray over marked areas + intake manifold,
I’ll Keep on update if any development occurs while testing out.After a long digging, it looks like my model uses only MAP sensor combined with IAT. (got no MAF signal too)
Pulled it out, cleaned.
It was covered with what seems like oil/petrol mix.Cleaned front area of the the TB plate. (it’s electronic, I didn’t want to mess with opening it by hand)
Had a try resetting the PCM / ECU and done the relearn procedure.
Disconneced the NEG bat cable, disconnected the POS bat cable, shortened them together for like a 10 min.
Although, I think I did it wrong and should’ve leave the POS terminal connected while shortening the NEG cable on it. (cause my radio channels memory stayed)Results at Idle:
STFT = 1.6
LTFT = – 8.6Results at 2K:
STFT = – 7.0
LTFT = – 4.72K results look worse than before, strange.
i’ll have to dig deeper.fuel pressure? – if so, looks like too high pressure (possible raptured FPR / bad vac line)
I tend to belive it’s some vacuum leak.. don’t like this plastic intake manifold idea.Any thoughts?
Results:
At 2K rpm (actually rpm seems like it was a bit floating up and down around 2k, but that could be my fault)First time 2k:
STFT = – 5.5%
LTFT = – 0.8%Second time 2k:
STFT = – 10.2%
LTFT = – 0.8%Idle:
STFT = 11.7%
LTFT = – 21.1%Check if your Ignition timing marks are spot on with a timing light, they could be off..
Also in my system the car wasn’t storing codes for tps sensor while not running, have you tried checking codes with a running car?
(btw in my case i had an obd1)After almost two years of trying almost everything.. now I can call it a FIX!
Reminder:
The Original problem was jerking hard when taking the leg off the gas pedal around 2K – 2.5K RPM, especially when vehicle was cold.The so what went wrong?
A series of problems:1) The original IACV was busted ( so replaced with Junk yard part)
2) The Ingnition timing was overly advanced and when I tried to set it by the factory timing makrs, the car would ping hard and won’t accelerate.
(I’ve bought a timing light to set properly and disabled the ECU, by shorting two connection terminals on the obd port)
Which made me suspicious about the third thing: The Timing belt alignment! (why else would a car run like crap by the factory marks??)3) Timing belt marks.. discovered the Camshaft was 1 tooth off.
4) That one was actually hard to find.. A TPS Sensor Connector had an abrupt contact, so I’ve bent a bit the “legs” of the connector and worked like a charm.
That’s it!
Extra info:
Important extra about OBD 1 and this antique TPS sensor:
Why I couldnt read that I had a tps code fault from the beginning? (code 12 here)
[u]for some weird reason that the ECU dosen’t store this specific code in the system!
All my pervious code tests were made when the engine was shut off.[/u]Discovered the code by pure luck when I adjusted the ignition timing (disabled the ecu – runs it in code read mode) and in the same moment the connection of the tps was bad.
Another symptom was that the engine ran “almost smooth” just a very slightly unstable rpm (not enough to show it on the rpm panelboard)
Which made me wonder back then, why it does it when it has 0 vacuum leaks + correct ignition timing + correct camshaft marks.
the lucky TPS code explained it all. :woohoo:Had a great battle over this one, now its over and im kinda bored.. but satisfied 😆 .
This case teached me so much about car mechanics and diagnostics, so it’s my duty to share this info here.
Thanks a lot to Eric The Car Guy, guys on this forum and many other Mechanics and Technicians over youtube and the web!
Also to BIG Thanks to good friends that helped me to get the job done.Every mechanic I had met with said it’s easier th throw it off the cliff than try to find the problem, or they just couldn’t reproduce it, or said something like “yeah it’s an old car and this is how they act, get used to it.” :blink:
A long one..Sorry.
Today I disassambled the ecu..again.
Inspected closely the parts, and measured resistances. Surprisingly all is within specs, and seems ok. The picture dramatized the look, yes some parts were overheated but they alright.
Well this is what I got until now:Cold car – Jerks hard around 2k-2.2k RPM, Light throttle. Most pronounced at 1,2 gears. (I guess overly lean)
Warm car – Much better, symptoms almost gone, hardly could be reproduced.As the focus is on cold, I’m ruling out the o2 sensor as possible cause. (open loop and it’s just 8 months old)
Testing again for vac leaks, could be something I missed. so far I’ve changed most of my vac hoses, the other 3 I left seem in good condition.I do hear some hissing around the throttle body, cannot pinpoint where..actually it sounds just like an IAC is letting through. I did sprayed water around the intake and the TB gasket injector o rings, nothing changed.
btw, my IAC is built in the TB and has no gasket.
The only thing that I did noitce, is when the car warms up fully, the hissing is almost gone, which is when the car runs better under load.
and..this car dosen’t have any EGR.p.s I remember that in the past, disconnecting my IAT sensor made the car run better. (engine checked on, probably ran on defaults) – the sensor was checked and tested as good, just in case.
Maybe another clue.. unrelated to vac leak..
In the past, as I chase down the problem i tried to set up the ignition timing with a timing gun via cyl #1. and spot on makrs. (prior disabled the ecu ofc)
But a weird thing happend back then, on under load test drive the car didn’t respond well to a gas, just pinged instead.
so I had to set up the timing by hearing and not by the mark, and it ran much better and pulling good. (advanced it a bit, no scale exist)
Someone said that this could happen because I’m using a 95 octane fuel, instead of 92, which the car was designed for..but I doubt it as a cause. (no 92 around)So I think, I should stick to chase a vac leak..maybe In another locations or trying crab cleaner instead of water. Is it possible for a leaky power steering pump produce a vac leak? (it has 2 vac hoses)
Any enlightments?when checking the fuel pressure regulator, start the car, remove the vacuum hose and watch the regulator closely for few minutes, sometimes it takes a while to wait before it’s spraying all around.
Yes it could.
anyways It would be great if you can borrow/buy an obd2 code reader that would pinpoint the problem, and help you in future.
Meanwhile try to locate the sensor and look if it got 2 or 3 cables connection.
if it’s 2 wires search in youtube how to test an Indutive cps sensor. (which I belive is yours)
if it’s 3 wires search for hall type cps sensor test.
