Surging/bucking while driving

[Jacobvarnum]

Hello,
I have a 1990 sho with 180,000 miles. For what it’s worth it say in a field for a decade or two. I have replaced radiator, thermostat, coil, plugs, battery, cleaned the intake, new iac, I believe it’s a new maf but I can’t remember.
Since I got it, it starts first time, it idles great, and it drives great. My issue is once it gets up to temp, it will intermittently cause a surge/buck. This happens whether I’m on the gas or not. It will sometimes happen after I shift from neutral in stop and go traffic, but sometimes it will happen 15 minutes into my 70mph drive with cruise control on. I’m really at a loss here, thinking about buying a new ecu since that seems to be something discussed in other similar posts.
Also, if I just keep driving it will eventually sort itself out. If I stop, revs bounce between 800-1000. I’ve been trying to pay attention to when it happens, but there doesn’t seem to be a pattern. Another thing is, if I shut it off while it’s doing it, it cranks but won’t start for a minute and then will fire right up and run great.
Let me know what you think and thank you in advance.

 

[Irish Pride]

Pull the codes and see what comes up. The symptoms lead me to believe that the MAF, Throttle Position Sensor, or Idle Air Control Valve is giving you problems. Codes will direct you where to look.

-Chad

 

[Jacobvarnum]

Pull the codes and see what comes up. The symptoms lead me to believe that the MAF, Throttle Position Sensor, or Idle Air Control Valve is giving you problems. Codes will direct you where to look.

-Chad

Thank you very much! I bought a Ford obd1 code reader, but I’m having issues with it actually testing. I’m connecting it correctly, I press the test button, get a solid arrow, then a solid square, hear a few clicks, then nothing. Is it just a faulty reader or did I mess something up? I’m going to try the paper clip method this weekend but I think the cel light is burned out. Will change out if I need to to get the codes.

 

[Irish Pride]

When you turn the Ignition switch to the run position the CEL will illuminate along with all the other cluster lights. If it doesn't light up then it's burnt out or you have a PCM issue.

-Chad

 

[luigisho]

Thank you very much! I bought a Ford obd1 code reader, but I’m having issues with it actually testing. I’m connecting it correctly, I press the test button, get a solid arrow, then a solid square, hear a few clicks, then nothing. Is it just a faulty reader or did I mess something up? I’m going to try the paper clip method this weekend but I think the cel light is burned out. Will change out if I need to to get the codes.

what code reader are you using? Some work well, some are spotty. Like Chad said above, failure to read any codes (including just the all good code) is usually a sign of a faulty computer.

 

[Jacobvarnum]

what code reader are you using? Some work well, some are spotty. Like Chad said above, failure to read any codes (including just the all good code) is usually a sign of a faulty computer.

It’s the innova 3145

 

[Jacobvarnum]

When you turn the Ignition switch to the run position the CEL will illuminate along with all the other cluster lights. If it doesn't light up then it's burnt out or you have a PCM issue.

-Chad

Ah you’re right, thank you, my cel works, gonna do the paper clip test now

 

[luigisho]

That model should work. Interesting

 

[Jacobvarnum]

That model should work. Interesting

For what it’s worth also, I can smell something burning when I get out of the car after my commute home. Smells like rubber burning? I know my belts are due but I don’t believe that’s what’s getting so hot

 

[luigisho]

huh. Usual suspects are oil on the exhaust/cats, electrical ( ), belts (maybe belt or pulley bearing fail), not sure what else is a normal rubber scent. A hose could melt but it would have to be touching something I would think.

 

[Jacobvarnum]

huh. Usual suspects are oil on the exhaust/cats, electrical ( ), belts (maybe belt or pulley bearing fail), not sure what else is a normal rubber scent. A hose could melt but it would have to be touching something I would think.

I would assume belts, I know they’re due, same with the pulleys. Would that affect the drivability that much?

 

[luigisho]

Well the belt would change power steering, cooling and charging. So maybe. Did this start after you attempted to repair or do maintenance?

You really need some sort of codes to get a pic of what could be malfunctioning that the computer sees. If you can see what the computer is showing then you can narrow the search field.

If you think it is the MAF you can unplug it and run it that way. It will throw a MAF code and run in limp home mode low on power but the bucking/surging should go away. If that does not work then it is likely not the MAF.

THe intermittent malfunction appears like a faulty sensor to me. (I can think of other things but that is just making a list of everything that makes a car run properly) Just have to narrow it down.

 

[Jacobvarnum]

Well the belt would change power steering, cooling and charging. So maybe. Did this start after you attempted to repair or do maintenance?

You really need some sort of codes to get a pic of what could be malfunctioning that the computer sees. If you can see what the computer is showing then you can narrow the search field.

If you think it is the MAF you can unplug it and run it that way. It will throw a MAF code and run in limp home mode low on power but the bucking/surging should go away. If that does not work then it is likely not the MAF.

THe intermittent malfunction appears like a faulty sensor to me. (I can think of other things but that is just making a list of everything that makes a car run properly) Just have to narrow it down.

Ok I tried the paper clip method, no luck. I’m sure I had it connected correctly, cel just stays on, no flashing.

 

[Jacobvarnum]

Ok I tried the paper clip method, no luck. I’m sure I had it connected correctly, cel just stays on, no flashing.

I also noticed today that the tach will occasionally go out, but necessarily at the same time as the surging. I also recently replaced the coil ~400 miles ago

 

[luigisho]

That sounds like a malfunction to me. You should at least get the all clear code either 11 or 111 depending on model year. If you have nothing then you have an issue somewhere. Especially if you don't turn the steering wheel and push the brakes during the test. That alone would throw a fail to execute during the test code. key on engine off and key on engine running to test codes

 

[Jacobvarnum]

That sounds like a malfunction to me. You should at least get the all clear code either 11 or 111 depending on model year. If you have nothing then you have an issue somewhere. Especially if you don't turn the steering wheel and push the brakes during the test. That alone would throw a fail to execute during the test code. key on engine off and key on engine running to test codes

Ok I ran it again.
KOEO: 953, 63, 67
KOER: 111

 

[Jacobvarnum]

Ok I ran it again.
KOEO: 953, 63, 67
KOER: 111

Also, it was very hard to start at temp. Cranking but no start, then would crank a little and give up, back to cranking normally no start, backfires a couples times, then after waiting a couple seconds, it’ll start right away

 

[luigisho]

it should have either 2 digit or 3 digit codes. not both

Was this happening before or after you replaced those listed components in the early post?

 

[zoomlater]

if you have a Gen 1, you should have two digit codes

 

[Jacobvarnum]

it should have either 2 digit or 3 digit codes. not both

Was this happening before or after you replaced those listed components in the early post?

This has been happening since I got it, so before. The two and three digit was weird to me also, I ran the test 3 times and that’s what came up.