whall

Dave,
On the HVAC side, by the brake booster, all of the lines were replaced and the vacuum is perfect to spec. Under the manifold was a 8-way plastic vacuum connector. I replaced this with a brass one that I had a local machine shop build. All of the lines going into this have also been replace. The above test is related to this side. I beleive the vacuum does not hold because it is connected to the manifold vacuum where when you shut the car off, the vacuum dissappears. Anyways, I am nearly certain that it is not vacuum related. It starts fine, idles fine for about 5 to 8 seconds then dies. If I rev it up to about 2 k, every couple seconds, the rpm instantly drops by about 1k rpm. Just like a one second ignition miss or a loss of fuel for a second - looking for any next checks. I am lost and want to get through this and get it running well again.
W

Vlocity

Warren:

At this stage I would also check relay number XVI (EZF) and relay numberXXV LH-Jetronic replacing each of them with a known good relay. I would also check BOTH coils to make sure you don't have one coil that went poop on you and is failing after the initial short warm up. You may also want to check both distributors and rotors.

Let us know what you find.

Ken

whall

Ken,
How do you suggest I check the coils, distributors and rotors? I have checked the coil wires and they are good. I only bought the car about 6 months ago but the coils look relatively new. However, I will replace all of the above if there is no simple check.

Bill Ball

Couldn't unplugging the MAF and observing no change mean the MAF is bad. I.e., it isn't working plugged or unplugged.

whall

Bill,
My understanding was that if the MAF was bad, unplugging it would make it run better for a short time (see comments above in this thread). I do not know but I do know that unplugging it made absolutely no difference to how the car ran - like crap. If I can not identify the problem fairly soon, I will start replacing things - MAF, coils, brains, etc but I would prefer to identify the source of the problem instead. Thanks
Warren

Vlocity

Warren:

I would exchange out the relays that I mentioned above first with a known good one. Your panel is full of relays such as the back up light relay and horn both which are interchangeable with the EZK and LH jetronic.

I take it that you are positive that the fuel pump is running. Have you bridged the relay? You can bridge the relay by pulling the relay from the Central Panel and then inserting a piece of wire with the ends stripped between pin 30 and 87. With the relay bridged you should hear the pump run when the key is turned to the on position.

One more thought. You might disconnect the battery for a half hour and then reconnect to allow the computer to "reset". Disconnect it at the ground.

Do you have a spark plug tester? It is just a lead with a bulb in it that you can place between your plug wire and your spark plug and will "fire" to prove to you that the cylinder is receiving spark. I would check a plug from each distributor. You can purchase one of these from a parts store.

Coils are coils, if you have a known good coil, exchange one out at a time... A lot of automotive stores can test your coils.

As for the distributors, I was just suggesting that you pull each cap and look for any moisture, obvious cracks etc. Also you can clean up the contact points with a small ignition file or just a piece of fine sandpaper. Check the rotor to make sure it is in tact and turning.

You have either a fuel problem or an electrical problem. The first step is to determine which.

Have you pulled any of the spark plugs to see what they look like to determine if the problem is on all cylinders or one bank? Does the car smell of gas and smoke as if it is running rich? I wouldn't buy any parts at this point until you have a little better diagnosis on fuel or spark issue. The above should help you with the spark issue.

Let me know what you find.

Ken

whall

Ken,
Thanks a lot for the insights. First, I have tried the relay switches earlier with no success. Second, no smell of fuel. The car runs quite normal for the couple second interval between misses so watching for spark will be difficult as it will spark for the most part. However, I will try this anyways. I do agree - it is spark or fuel and I need to determine which. As for smell of fuel or smoking - no. Either the car is running out of fuel or it is losing spark - it is not running rich. I will try bridging the relays as suggested to ensure that the pump runs. However, I dont see the car running with out a pump. If I start the car and keep revving it, it will stay running. It will miss and drop 1000 rpm but If I keep revving, I can keep it running - this would indicate to me that the fuel pump is running - maybe intermittently though?
Warren
Thanks again for all suggestions!

intrepidjohnson

I had the same problem and a new fuel pump corrected it.

Bill Ball

I'd like a better explanation of how pulling the plug on the MAF and seeing no difference in how the car runs rules out the MAF. My layman's interpretation would be MAF is not working so car runs like crap. Maybe John Speake is reading and will jump in.

SharkSkin

Warren, some other possibilities are that the tach signal is intermittent to the fuel relay, the fuel relay is defective, or the connection to the pump is intermittent. If you have to have your foot on the pedal to keep it running, you could tie-wrap a long piece of tubing to the fuel pump and listen to it run while you keep the car running. It can be a little frustrating troubleshooting systems that only work when the car is running.... if it runs like crap.

You don't have the dreaded green wire, do you? I don't know when they quit using those, but mine kept me entertained for a while until I found the problem. I had similar symptoms, but it was due to the aged green wire shifting around and shorting intermittently. This only started happening after I moved it, while working on the nearby AC wiring.

John Speake

Warren,
You can check the fuel system flow rate with the test described in the workshop manual. It is checked at the return to the fuel tank.

Also worth checking the fuel pressure on the end of the rail if you can borrow a gauge.

I assume you have changed LH and EZK relays, as well as the fuel pump one ?

No change when you disconnected the MAF does not mean the MAF is OK. The car may already have gone into limp home mode. How many miles on the car ?

Vlocity

Warren:

One other thought....you indicated that you have been the owner for a little over 6 months, do you know the status of your timing belt? You can not rely on the tensioner light ...someone may have disconnected it. It might be possible for your belt to have slipped a tooth or two and still run but act as you described. Short of pulling the front covers off you could borrow or buy a compression tester and make sure that you have good compression. (an out of time motor will reflect a low compression probably on one bank).

Again...just a random thought. You can search the threads for how to conduct a compression test.
An 85 should be in the 180-190 range plus or minus 10%.

Regards,

Ken

whall

Will Check fuel pressure, then dist caps, rotors, etc. I own a compression tester and can check myself but given the the power is normal for short intervals with a massive miss every 4 to 10 seconds, seems unlikely to me? Will update at the end of the day after the suggested checks. John, the car has 60k miles. The deterioration was over the period of about one week. It had a slight miss at deceleration, then the miss got worse until I could barely drive.
Thanks for your help - will update.
Warren

Jeff McVicar

Dude I have the exact same thing going on. I will start it up and either it will run for 2 seconds and turn off all together or it will idle at 1200 and shut completely off and catch again at about 400 rpms ....continue to 1200 and drop off again. In almost exactly 2 second intervals. I was messing with the relays and it corrected it for a short time. I think I need toclean all the contacts in the relay box......... I just havent got aroundto it yet. I'll be watching you also to see if you get yours right in the mean time. Oh yeh it was the fuel relay I was messin with.

whall

Jeff,
I did try changing the fuel relay with no change in the problem. I will keep you updated as I check things. Your description sounds identical to mine. My guess right now is fuel but I will know more shortly.
W