I'm new to the board, but been lurking for years now, and really enjoy this board. I have an 84 GN with a 87 drive train I installed in 96. I restored the car two years ago, including a mild engine rebuild. I have about 3000 miles on the car since the restoration, without much trouble until recently.....
When I put a load on the car, (driving) around 4100 rpm the engine cuts out.
I get some knock, 1-6 on the scan master, when the stumble occurs, acts like a rev limiter. Never get a check engine light, the light does come on if I unhook a sensor, so the light is working.
I had the stock MAF go out on me about 8 weeks ago, replaced it with a 3" and translator, car did fine for about 100 miles then the stumbling started.
Here is what I've done with no change to the problem,
Replaced:
Crank sensor, ring looks good, gap at .025".
Fuel filter.
Walbro 340 pump, added hot wire kit. Old pump was a Red Armstrong, about 8 yrs. old.
Upgraded to 60#motrons W/ TT chip. Used, bought from a good source (also reset switches in translator box, reset computer)
Spark plugs, old ones looked good gap at .033" AC43ts
Plug wires
Swapped parts from known good parts:
Ign. module with coil pack
computer
ESC
MAF, a 3.5" then a stock one
Cam sensor cap
02 sensor
If I rev the engine fast and in park I can duplicate the stumble at 4100rpm.
If I rev it semi fast, it revs fine/normal, scan master numbers look good.
Here are my numbers from the scan master, with the car in park.
At Idle:
02-varies-0 Kr
AF-06
LB-38-41
Bat 13.8
Int-125
BL-110
MPH-00
CLT-160
Ats-116
R-825
TPS-.42
IAC-10
CC-climbs then starts over
Mal-00
Duplicating the problem in park, with a quick "stab" to the gas:
02-varies, 200-700 (when stumbling) KR-2-7 (when stumbling) will climb if I don't let off
AF-140
Lb-200
Bat-13.5
Int-128
Bl-124
Mph-00
Clt-168
Ats-136
Rpm-4250
Tps-3.64
Iac-53
CC-16- will climb
Mal-00
I've checked my air duct work, no holes.
I recently TIG welded by exhaust manifolds.
Compression check is 150 psi on every cylinder.
Unplugged computer wire, cranked engine with valve covers off, rockers are all moving the same distance, (by eyeball)
fuel pressure is 43# with line off, I've adjusted up to 50# down to 30#
Fuel pressure increases with boost 1to1.
Have good grounds, have a wire going to left fender to bell housing, to A-arm bolt. Also have gas tank grounded to frame.
All vacuum hoses replaced at restoration. 15 Hg. in. at Idle
Boost gauge and Alcohol is tapped off the line by the left side of coil pak.
Egr was filled when rebuilt. Heads from Champion.
Have HanR motor mounts. Looked all over for anything rattling causing a false knock.
Looked for shorted, open wires, can't find any.
I will accept any ideas and will try anything to remedy this problem.
I appreciate your efforts,
Thanks.
Brent
Also, If anybody has a set of center caps for the stock 84 rims, I'd be interested in buying, someone stole mine off my car when it was in my shop.
I hope it wasn't someone I know....
When I put a load on the car, (driving) around 4100 rpm the engine cuts out.
I get some knock, 1-6 on the scan master, when the stumble occurs, acts like a rev limiter. Never get a check engine light, the light does come on if I unhook a sensor, so the light is working.
I had the stock MAF go out on me about 8 weeks ago, replaced it with a 3" and translator, car did fine for about 100 miles then the stumbling started.
Here is what I've done with no change to the problem,
Replaced:
Crank sensor, ring looks good, gap at .025".
Fuel filter.
Walbro 340 pump, added hot wire kit. Old pump was a Red Armstrong, about 8 yrs. old.
Upgraded to 60#motrons W/ TT chip. Used, bought from a good source (also reset switches in translator box, reset computer)
Spark plugs, old ones looked good gap at .033" AC43ts
Plug wires
Swapped parts from known good parts:
Ign. module with coil pack
computer
ESC
MAF, a 3.5" then a stock one
Cam sensor cap
02 sensor
If I rev the engine fast and in park I can duplicate the stumble at 4100rpm.
If I rev it semi fast, it revs fine/normal, scan master numbers look good.
Here are my numbers from the scan master, with the car in park.
At Idle:
02-varies-0 Kr
AF-06
LB-38-41
Bat 13.8
Int-125
BL-110
MPH-00
CLT-160
Ats-116
R-825
TPS-.42
IAC-10
CC-climbs then starts over
Mal-00
Duplicating the problem in park, with a quick "stab" to the gas:
02-varies, 200-700 (when stumbling) KR-2-7 (when stumbling) will climb if I don't let off
AF-140
Lb-200
Bat-13.5
Int-128
Bl-124
Mph-00
Clt-168
Ats-136
Rpm-4250
Tps-3.64
Iac-53
CC-16- will climb
Mal-00
I've checked my air duct work, no holes.
I recently TIG welded by exhaust manifolds.
Compression check is 150 psi on every cylinder.
Unplugged computer wire, cranked engine with valve covers off, rockers are all moving the same distance, (by eyeball)
fuel pressure is 43# with line off, I've adjusted up to 50# down to 30#
Fuel pressure increases with boost 1to1.
Have good grounds, have a wire going to left fender to bell housing, to A-arm bolt. Also have gas tank grounded to frame.
All vacuum hoses replaced at restoration. 15 Hg. in. at Idle
Boost gauge and Alcohol is tapped off the line by the left side of coil pak.
Egr was filled when rebuilt. Heads from Champion.
Have HanR motor mounts. Looked all over for anything rattling causing a false knock.
Looked for shorted, open wires, can't find any.
I will accept any ideas and will try anything to remedy this problem.
I appreciate your efforts,
Thanks.
Brent
Also, If anybody has a set of center caps for the stock 84 rims, I'd be interested in buying, someone stole mine off my car when it was in my shop.
I hope it wasn't someone I know....