Judder on LPG
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Judder on LPG
OK, my P38 is exhibiting the most peculiar anomaly:
It's a 4.6 with OMVL Dream 21 LPG.
Runs perfectly on petrol. Runs perfectly on LPG at light to moderate loads. But:
When under heavy load between 3500rpm and 5000rpm, it judders pretty badly. Perhaps not as regular and harsh as a total misfire, but very very jerky nonetheless.
I've done some diagnostics with the LPG software and an OBD-II reader, and the following are true:
1. The Injector times go wild when it judders
2. The MAF reading goes wild (is 80-90 when on petrol, jumps up to 270 when on LPG!)
3. TPS is steady
I can't understand why it should be perfect on petrol, yet not OK on LPG.
Any ideas?
Thanks,
Chris.
It's a 4.6 with OMVL Dream 21 LPG.
Runs perfectly on petrol. Runs perfectly on LPG at light to moderate loads. But:
When under heavy load between 3500rpm and 5000rpm, it judders pretty badly. Perhaps not as regular and harsh as a total misfire, but very very jerky nonetheless.
I've done some diagnostics with the LPG software and an OBD-II reader, and the following are true:
1. The Injector times go wild when it judders
2. The MAF reading goes wild (is 80-90 when on petrol, jumps up to 270 when on LPG!)
3. TPS is steady
I can't understand why it should be perfect on petrol, yet not OK on LPG.
Any ideas?
Thanks,
Chris.
--
Series IIA 4.6 V8
R/R P38 4.6 V8
R/R L405 4.4 SDV8
Series IIA 4.6 V8
R/R P38 4.6 V8
R/R L405 4.4 SDV8
Re: Judder on LPG
Any EFI system depends on a reliable tach signal from the ignition. And a good clean supply of battery volts, including the ground. Corruption of either could cause your problemsChrisJC wrote:OK, my P38 is exhibiting the most peculiar anomaly:
It's a 4.6 with OMVL Dream 21 LPG.
Runs perfectly on petrol. Runs perfectly on LPG at light to moderate loads. But:
When under heavy load between 3500rpm and 5000rpm, it judders pretty badly. Perhaps not as regular and harsh as a total misfire, but very very jerky nonetheless.
I've done some diagnostics with the LPG software and an OBD-II reader, and the following are true:
1. The Injector times go wild when it judders
2. The MAF reading goes wild (is 80-90 when on petrol, jumps up to 270 when on LPG!)
3. TPS is steady
I can't understand why it should be perfect on petrol, yet not OK on LPG.
Any ideas?
Thanks,
Chris.
My guess is the tach signal. Have you a method of logging it?
Dave
London SW
Rover SD1 VDP EFI
MegaSquirt2 V3
EDIS8
Tech Edge 2Y
London SW
Rover SD1 VDP EFI
MegaSquirt2 V3
EDIS8
Tech Edge 2Y
Thanks chaps.
The 'tach' signal is OK. I know this because the rev counter is stable on the gas diagnostic software.
I wondered about the leads. I'm reluctant to fork out for a new set without proof, as they're dear for a Thor engine, and they are less than a year old. Mind you, they were 'pattern' leads rather than super-duper expensive ones. Rimmers want £101.22 for a genuine set!!
I think I'll strap a video camera under the bonnet and go for a drive. See if there's any evidence of tracking.
Chris.
The 'tach' signal is OK. I know this because the rev counter is stable on the gas diagnostic software.
I wondered about the leads. I'm reluctant to fork out for a new set without proof, as they're dear for a Thor engine, and they are less than a year old. Mind you, they were 'pattern' leads rather than super-duper expensive ones. Rimmers want £101.22 for a genuine set!!
I think I'll strap a video camera under the bonnet and go for a drive. See if there's any evidence of tracking.
Chris.
--
Series IIA 4.6 V8
R/R P38 4.6 V8
R/R L405 4.4 SDV8
Series IIA 4.6 V8
R/R P38 4.6 V8
R/R L405 4.4 SDV8