stumble right off idle(89 lancer shelby)

[v62go]

no codes but it has a stumble right off idle. it sit for a long time and I had to replace the fuel pump. it seems to hit a brick wall when it goes into boost also.. any help will be appreciated.

[ajakeski]

It could be that additional fuel system components need attention. If the fuel filter is old , it should be changed. Check the injectors and rubber fuel lines.

Look in the distributor and see if the shutter wheel is loose. This would cause erratic spark and fuel signals to be sent to the computer.

[v62go]

I haven't changed the fuel filter yet so that might be the problem.. another question, will the speedometer not working cause any problems?

[ajakeski]

I haven't changed the fuel filter yet so that might be the problem.. another question, will the speedometer not working cause any problems?

It shouldn't but it could be a sign that the Vehicle Speed Sensor (VSS) is bad. Having a bad VSS could cause the car to stall when coming to a stop.

[Vigo]

Did you drive/own it before the long sitting period?

Falling on it's face in boost could be a lean condition. Do you have any kind of AFR monitoring like a wideband?

[zin]

Get a scan tool on it if you can. The boost thing sounds like the MAP sensor could be bad and sending an "overboost" voltage... something that won't easily throw a code, but will cause problems (ask me how I know!). Also, temporarily install a fuel pressure gauge where you can see it while you drive, just duct tape it to the windshield if you have to, so you can see if the fuel pressure is what is causing the problem(s).

Is the stumble there all the time off-idle, or just when it's cold?

Do fix the VSS as I have heard of some weird problems that "fix themselves" when the VSS is working correctly, though it really shouldn't be able to cause the problems you're describing, it's just an easy fix that might save some more trouble down the road... and who doesn't like a working speedo anyway, right?

Between the scan tool and fuel pressure gauge, you should be able to figure it out pretty quick.

Mike

[GLHNSLHT2]

check the cam timing too. My 87 Shelby Lancer would fall on it's face leaving the line, I got beat by a nissan cube. Cam timing was retarded a tooth.

[v62go]

Its bone stock and has been sitting for 20yrs. Im going to change the fuel filter next . Anybody have a picture and the location of the vss? Thanks for all the replies and help.

[going4speed]

No good way to take a picture of the vss. Best to remove the airbox and it's sort of under the turbo on top of the trans. Held in with 1 10mm bolt if I recall on the passenger side. I take these out the top but perhaps it's easier out the bottom but I dont think so. Its a bear to get to and is likely well stuck in there after that amount of time sitting. They can be had on ebay nos pretty cheap. I think in fact I just picked one up for about $25.

[v62go]

the speedo is working now but I noticed it will boost fine cold but when the engine gets warm it acts up under boost.. any ideas??

[going4speed]

With no codes that's a tough one. Could be coolant temperature sensor, air temp sensor, collapsing vacuum lines due to heat, lean condition....

[acannell]

pull vac line off fuel pressure regulator and see if gas comes out of it

[v62go]

It boost great when its cold but soon as it gets any heat on the motor it starts acting up when I run it up into boost.

[zin]

If the MAP is off (reading higher than it is), it will add extra fuel, when an engine is cold, it will like/tolerate more fuel, but not when it's fully warmed up...

Have you confirmed you have an accurate MAP?

Mike

[going4speed]

I also like to make sure to tee my map and fuel pressure together to the vacuum source

[3Bar_Mopar]

Replace all vac lines, fuel filter, new VSS, new MAP, new TPS, new plugs, wires, check FPR for gas, check for the cat being clogged...mice in the exhaust, lol...cam timing, etc. I had a car that ran like crap in boost when: spark plug wires were arcing, plugs were gapped too much, TPS was bad, MAP line had a leak, FPR diaphragm was ruptured.

[going4speed]

Compression and leak down numbers?

[Ondonti]

VSS is an extra problem but not your main problem. Lack of VSS messes up decel, coasting, and idle coming to a stop.

Its probably lean misfiring as Vigo said above.

[v62go]

it finally thru a code(check engine light)now it will rev to about 2500 rpms and acts like it hits a 2step... is there a easy way to check codes on these cars?

[GLHNSLHT2]

Yep, read this page http://minimopar.net/fault/index.html

You're in limp-in mode.

[v62go]

code 13

[Gaboon]

code 13
Map sensor vaccum.

Check the vaccum line leading from the MAP sensor.

[GLHNSLHT2]

Check them all from the intake. Also don't forget the one from the Baro solenoid to the MAP too. if you need replacement nylon in stock size you can order it here cheap

http://www.automationdirect.com/adc/Shopping/Catalog/Pneumatic_Components/Flexible_Pneumatic_Tubing_-a-_Hoses

The small stuff is 5/32 and the larger stuff is 1/4". I switched to Polyurethane on my stuff, it lasts longer, is more flexable, and flows just a hair better in the same size. But you have to be careful to keep it below 180-190 degrees as it get's soft. So basically it can't directly touch the head. So I'm just careful about where I route it.

Here's my 2 piece vac setup with Poly, Nylon would look similar
https://scontent-sea1-1.xx.fbcdn.net/hphotos-xpf1/v/t1.0-9/s720x720/1380777_3458163868232_1415166874_n.jpg?oh=3755378d fe71e8636f8b6b3dcd95f90e&oe=55FDE023

And then my more factory style 88+ vac setup.
https://scontent-sea1-1.xx.fbcdn.net/hphotos-xat1/v/t1.0-9/1186716_3458435915033_1548688560_n.jpg?oh=53f77525 ff984f0bfffcf6515aaed155&oe=55C5395D

[ajakeski]

The fuel pump in my Lancer Shelby died today. It would start, run and then stumble to death when you tried to drive it.
a new pump fixed the issue.
Have you checked the fuel pressure on you car? I still think you have a bad fuel pump, especially after reading that the car sat for a long time.

[v62go]

I put a new pump in it.