Running Rough

[tommyb]

Sold my 84 SVO and transferred ownwership at the Minneapolis/St. Paul Airport today new owners who are nice as could be! Car and particularly the engine have been running smooth and strong all Spring as I have been driving it occasionally preparing for this day. I just got a text from the new owner that said approximately 20 miles from the airport it started running rough and down on power. He changed the spark plug wires but that was no help. He states that it feels like a dead cylinder and will pull the plugs tomorrow. Eventually made the trip from Minneapolis to Chicago area. Any ideas that are possibilities that I may not be thinking of are much appreciated. I know this description is not very specific but the best I can do.

Tom

[MikeFleming]

Check fuel pressure - re: high-pressure fuel pump.

[Meotchh]

Fuel, Air, Spark. The likely item to fail would be the pump.

[tommyb]

High pressure is in the tank, right I just replaced the frame mounted pump a couple of years ago.

[majestic]

High pressure is in the tank, right I just replaced the frame mounted pump a couple of years ago.

Other way around, I think.

[MikeFleming]

Originally the dual-pump systems (84/85) models used one low-pressure (up to 6 PSIG) feeder pump in the tank and one high-pressure chassis-mounted pump mounted on the inner frame rail near the fuel filter. Both of them seemed to fail at about the same rate although the low-pressure pump failing didn't keep the car from running.

A common mod is to bypass the chassis-mounted pump and install the typical 86+ single in-tank high-pressure pump and associated wiring.

Rough running could be due to an about-to-fail fuel pump (low pressure), clogged filter (low pressure), air leaks, clogged injector(s), jumped timing belt, etc.

The new owner will need to do some diagnostic tests to track it down: compression test, check fuel pressure, check cam timing, EEC code test, etc.

[tommyb]

Mike, He'll figure it out, seems like a very sharp guy, I was just trying to help, timing belt is almost new fuel filter pretty new unless I got some bad gas, high pressure fuel pump pretty new, car was driving great for me at the handoff, I just feel bad cause it had been running so good recently, I guess anything can happen to a 34.5 year old car?

Thanks!

Tom

[rodster]

Mike, He'll figure it out, seems like a very sharp guy, I was just trying to help, timing belt is almost new fuel filter pretty new unless I got some bad gas, high pressure fuel pump pretty new, car was driving great for me at the handoff, I just feel bad cause it had been running so good recently, I guess anything can happen to a 34.5 year old car?

Thanks!

Tom


Yea, that's a bummer but you just never know with older cars, especially SVO's! Even restored cars can have issues. Hopefully the new owner is a car guy and understands and finds a easy fix. Lot's of great folks here to help out.

[Laredo]

Did he mention if the misfire occurs at idle, under load, or both?

[tommyb]

I don't remember him mentioning all those specifics, yes he is a car guy and hope to hear his findings soon, he is our newest member but has not posted yet

[Dougs40]

Good morning all,
i bought Tom’s 84 SVO a while ago. My wife and I drove it from Minneapolis to a southwest suburb of Chicago. The car ran great for the first 20 miles. Suddenly it started to shudder and run rough. At first thought I was guessing ignition. We finally stopped and I was able to purchase plug wires. Those didn’t help. We pressed on driving at about 50 miles per hour. Finally made it home that evening. I wasn’t really able to work on the car right away. When I could I went for the obvious things. Plugs, wires, cap, rotor. Timing, fuel filter. The fuel pressure was right on. I replace the TIF, cleaned the IAC. Swapped out the coil as I had an extra known good one. Checked vacuum hoses, electrical connections. I adjusted the TPS, the car started right up all the time but still had a miss all through the power band. I did a compression check all cylinders were around 140, solid engine. I looked at the cam and valve springs. I ordered 4 replacement injectors and finally put them in yesterday. Fired the car up and it runs like a dream! Now o get down to some fine tuning. I want to thank Tom for everything, his concern and support. My wife is very happy and excited to drive and enjoy it. Thank you all for the support!

[Laredo]

Thanks for the update! That's a really nice ride. Please keep us posted on your "fine tuning" or any other news, updates, upgrades, etc.

[rodster]

Interesting, so a bad fuel injector? Any way to diagnose that problem earlier? I would have thought ignition too.

Glad you got it running good again, keep us posted on your progress and enjoyment.

[Dougs40]

Thank you for the support! I ohmed the injectors out. All were the same, they all hit when the engine was running. I would have had to make a rig to test them for spray, so since they would have been out for that decided to start fresh and put new ones in. I’ll run a smoke check soon to button up any vacuum or air leaks. I had an 86 SVO in 88 and really enjoyed it. This one puts the same smile on my face! Will keep you all posted.

[rodster]

Thank you for the support! I ohmed the injectors out. All were the same, they all hit when the engine was running. I would have had to make a rig to test them for spray, so since they would have been out for that decided to start fresh and put new ones in. I’ll run a smoke check soon to button up any vacuum or air leaks. I had an 86 SVO in 88 and really enjoyed it. This one puts the same smile on my face! Will keep you all posted.

Interesting, kind of what I thought. No simple way to diagnose them, just one of those of parts that are easier to replace and check the results I guess.

Had my 84 out today and yep, puts a smile on my face every time..... well every time it's running good and no problems! Even had a few 'thumbs up' today so there are still other people out there that remember them.

Good luck and enjoy your new ride!

[Meotchh]

Good morning all,
i bought Tom’s 84 SVO a while ago. My wife and I drove it from Minneapolis to a southwest suburb of Chicago. The car ran great for the first 20 miles. Suddenly it started to shudder and run rough. At first thought I was guessing ignition. We finally stopped and I was able to purchase plug wires. Those didn’t help. We pressed on driving at about 50 miles per hour. Finally made it home that evening. I wasn’t really able to work on the car right away. When I could I went for the obvious things. Plugs, wires, cap, rotor. Timing, fuel filter. The fuel pressure was right on. I replace the TIF, cleaned the IAC. Swapped out the coil as I had an extra known good one. Checked vacuum hoses, electrical connections. I adjusted the TPS, the car started right up all the time but still had a miss all through the power band. I did a compression check all cylinders were around 140, solid engine. I looked at the cam and valve springs. I ordered 4 replacement injectors and finally put them in yesterday. Fired the car up and it runs like a dream! Now o get down to some fine tuning. I want to thank Tom for everything, his concern and support. My wife is very happy and excited to drive and enjoy it. Thank you all for the support!

Great work! Welcome to the club. Is it too late to consider coming out to Sturgis next month for SMR?