Pretty weird behaviour with my 89 XJ (Stumbling etc.)

Hey guys,
i bought a great XJ from 89 two weeks ago.
I drove it 250km home and except from some rust it looks great. Just needs some love.

Fist thing i did on the technical side of things, was to renew the Sparkplugs (Champion) the Wires, the Cap and the Finger.

Else i did Tips 1-5 from Cruisers Homepage.

I rebuilt the Cables to and from the Batterie, Ground, Starter Motor, added two seperate grounds as per Cruiser.

Got rid of faulty cables, cleaned every connector i could get my hands on, cleaned the Ignition Coil on the inside and put some Contactgrease inside.

Now what is wrong?

At around 1-1.5k rpm and above the jeep stutters and missfires like crazy, it ran 250km back home just fine, was stumbeling slightly at around 2k on the highway, but accelerating completely worked and it was nice to drive.

Now i cant even drive since it stutters so bad that its unbearable.

Yesterday i installed a FelPro Gasket since the Valvecover was basically just attached with RTV and i swapt the "Frontpart" of the Vacuum Harness, to the Cover and such, after that i tried it again.

It starts, when i rev it to 1-1.5k it stutters and a relay (picture attached) made a spar, just once, accelerating again and again didnt cause a spark or anything, yet it still accelerates like shit.

I tried everything in P btw. didnt want to drive it like that, yet i drove back and forth a bit and you cant drive it like that...

Anyone any idea what i could check next?

Pictures and a Video inside:
https://drive.google.com/drive/folders/157s7qYiyzv3iQNeY8jsAXMOMuGTboH-F?usp=sharing

You need to test the fuel pressure with a gauge.

31 PSI and when you pull the vacuum line from the fuel pressure regulator, the pressure should jump to 39 PSI.

cruiser54 said:

You need to test the fuel pressure with a gauge.

31 PSI and when you pull the vacuum line from the fuel pressure regulator, the pressure should jump to 39 PSI.

Click to expand...

Just ordered one, should arrive later.
Plug it on the Fuel rail and then start?
At idle or under load?

Thanks for your continous help!

Clean your Intake sensor thats on the throttle body. IAC

Also can confirm your TPS is adjusted correctly. I dont recall what the testing permeameters are though.

My 88 was doing the same thing for a while. Would studder and chug and backfire like crazy.

I can just remove the iac right?
Can i just use breakcleaner on it or what should i use?
The TPS is going to get done tomorrow when i figure out my stupid ohm meter

Use throttle body/carb cleaner. Make sure you clean out the bore in the TB as well. Carefully check the o-ring. Remove the intake tube so you can access the entire port. Also clean the throttle plate and bore. Use a rag to wipe it all down.

For fuel pressure, check at idle first. You can then rev the engine to make sure it holds at 2000-ish rpm.

UPDATE:

I meassured the grounds, pretty steady 0.8-9 overall regardless of how much i wiggle, 0.4 at the DipStick.
I tried to set my TPS, i cant get a hint of a voltage, i plug my multimeter in, put it in the b (ground) a (positive) and i get readings around 0.30.0 mv wich in my opinion should be wrong...
To check if my multi is broken i tried it at a AA battery and i get 1.6v out of it so i guess its working correctly, is it possible that the TPS is broken or should i still get some value out of it since its plugged in the harness?

I checked the VacLines, for now they look good, still need a Vac Tester, Fuel preassure i will do later, yet i found that if i accelerate FAST like i step on the throttle up to 3/4k i dont have any hesitation or stutter, if i slowly increase then the stutter is imminent at around 1-1.5k...
Theres a video -> https://drive.google.com/drive/folde...xq?usp=sharing
There is also a scratching noise all throught the video but especially when im at the dip stick area, is that normal? the ignition?

UPDATE2:

I Testet the Fuel Pressure.
If i just let it Pump on KeyOn it goes up to around 34 psi
If i start the engine it goes to a perfect 31, if i unplug the Vaccum hose from the Fuel Pressure Reg it goes up to 39
If i rev the engine, it stays at 39, like it doesnt move up a bit just 39 and i get stumble and missfire again...

make sure the vacuum hose from the throttle body to map sensor on the firewall isn't broken or leaking. back probing the tps sensor is really difficult sometimes. i usually use t pins to get in there better. you an try unplugging the 3 pin tps sensor and see if it helps any.

the automatic transmission will have 2 connectors at it. 3 pin for ecu and 4 pin for tcu.

did you remove the distributor at all during your service?

something looks fishy with your map vacuum hose. there is a clear hose hooked up thats T-ing into another vacuum line. and unless the euro spec was different there is only one port drilled on the throttle body.

90xj06 said:

something looks fishy with your map vacuum hose. there is a clear hose hooked up thats T-ing into another vacuum line. and unless the euro spec was different there is only one port drilled on the throttle body.

Click to expand...

Good catch!!

n3squ1ck: The vac line on the bottom of your throttle should go to the MAP sensor (from the pic it looks OK) Where does the upper one go?

On my US spec XJ, that hole is plugged like 90xj06 says. Part of the "fitting" has a bump that fits into that hole to ensure the line stays connected. Make sure it's not leaking. You may want to check out Cruiser54 tip #31.

Also, where is the line coming off your cruise control servo going? On my '88, it goes back through the firewall to a vent valve on the brake pedal. When you press the brake, the brake switch shuts off the CC and the valve vents the servo to the atmosphere to release the vacuum.

Saudade said:

Good catch!!

n3squ1ck: The vac line on the bottom of your throttle should go to the MAP sensor (from the pic it looks OK) Where does the upper one go?

On my US spec XJ, that hole is plugged like 90xj06 says. Part of the "fitting" has a bump that fits into that hole to ensure the line stays connected. Make sure it's not leaking. You may want to check out Cruiser54 tip #31.

Also, where is the line coming off your cruise control servo going? On my '88, it goes back through the firewall to a vent valve on the brake pedal. When you press the brake, the brake switch shuts off the CC and the valve vents the servo to the atmosphere to release the vacuum.

Click to expand...

the dump valve is still hooked up. its the larger vacuum hose in the loom. but typically the vacuum feed to the cruise servo is fed from the passengers side vacuum tank in the bumper. so it looks to be taping off directly from the manifold.

however this would not cause a stumbling issue.