97 850 non turbo wagon stumbling/hesitating

Seankevinorourke · Post by **Seankevinorourke** » 09 Aug 2018, 21:05

I have an issue with my 850 wagon non turbo 5 cylinder fwd . It hesitates under light pedal pressure. I’ve replaced the fuel filter, injectors, MAF, plugs, TPS,( all high end parts) cleaned throttle body ( off car) cleaned idle control valve ( off car). I fixed obvious vacuum issues and had a smoke test for vacuum leaks ( none found) I serviced the transmission and it is not slipping although it will down shift randomly at very low speed ( like 20 mph). It idles great. If I “ get on it” it’s fine... If I’m just cruising and barely give it a bit of gas, it’s stumbles. It doesn’t matter what speed. The car did sit for a couple of years but did not do this when I got it back on the road a few months ago. It has gradually gotten worse. I did all of this work after it started giving me the business. No codes. Paid for a full scan.Totally stumped. What say you guys?

Post by **jreed** » 10 Aug 2018, 05:00

Have you had a chance to check the engine coolant temperature sensor and wiring? If it's giving a falsely high resistance reading due to sensor failure or corrosion on the electrical connector pins, it could cause the engine computer to read lower engine temperature than actual and cause it to give more fuel than needed.

Post by **erikv11** » 10 Aug 2018, 07:51

Probably not the cause but to be sure: you put in a Bosch MAF?

Seankevinorourke · Post by **Seankevinorourke** » 10 Aug 2018, 09:09

jreed wrote: 10 Aug 2018, 05:00 Have you had a chance to check the engine coolant temperature sensor and wiring? If it's giving a falsely high resistance reading due to sensor failure or corrosion on the electrical connector pins, it could cause the engine computer to read lower engine temperature than actual and cause it to give more fuel than needed.

I checked wiring and cleaned connections and looks to be good. The gauge reads consistently. Beyond that I'm not sure how to check if it's bad. I forgot to add that when I was getting the car ready to put back on the road, I had the water pump replaced as it was why it was not running as well as timing and drive belts. Also had brakes and right C/V axle done. I replaced the coil as well.
The only thing I have not replaced are the cap and rotor or spark plug leads. I did clean the cap and rotor. But it idles fine and revs good in park. So far I've got well into 5 grand on this car.

Seankevinorourke · Post by **Seankevinorourke** » 10 Aug 2018, 09:17

erikv11 wrote: 10 Aug 2018, 07:51 Probably not the cause but to be sure: you put in a Bosch MAF?

It's a Bremi part # 1275749

Post by **scot850** » 10 Aug 2018, 11:35

These cars just don't like to play with other branded MAF's for some reason.

2 other things to check:

1) Did you replace the fuel pump relay? You can try removing the relay (in the rear section of the fuse box by the windshield and there are instructions on here which terminals to short with a paper clip.
2) Check the routing of the wiring of the cam sensor which is sited below the distributor. If it is routed too close to the distributor the distributor blanks the signal for the cam sensor.
3) As suggested check the wiring connector for the engine coolant sensor. Especially check the connector by the power steering pump which is well know to disintegrate with age.
4) Check the fuel pressure at the injector rail. should be around 43psi.

Neil.

Seankevinorourke · Post by **Seankevinorourke** » 10 Aug 2018, 11:56

Will do Thanks. I’m also wondering if it’s the fuel damper.

Post by **erikv11** » 10 Aug 2018, 12:40

Seankevinorourke wrote: 10 Aug 2018, 09:17
erikv11 wrote: 10 Aug 2018, 07:51 Probably not the cause but to be sure: you put in a Bosch MAF?
It's a Bremi part # 1275749

You can check the MAF by unplugging it before you start the car, then run it with the MAF unplugged. This will set a MAF code (CEL) but you can reset that. If the symptom goes away with the MAF unplugged, you found it.

Even if the Bremi MAF is working now, expect it to give you trouble.

Post by **misha** » 10 Aug 2018, 14:54

Seankevinorourke wrote: 09 Aug 2018, 21:05 ...I’ve replaced the fuel filter, injectors, MAF, plugs, TPS,( all high end parts)...

ALL sensors MUST be OE or OEM if you want the car running.

What high end parts?...Bremi Maf?!
It would run better without it than with it.

Filters...Mann,Bosch,Delphi,Knecht.
Plugs....cheap Bosch or NGK single prong copper ones correctly gapped or Volvo triple prong ones.
Sensors....oem Bosch,except ECT which is SWF(Valeo)...at least Vernet should be used and nothing else.

I suspect that you have the problem with only parts you didn't replaced....Bosch cap & rotor.
If cables are Bougicord(original) leave them alone....they are fine.
There is possibillity that you have bad tps or failing fuel pump or it's relay.

Does the car running rich...black smoke from the exhaust?

Seankevinorourke · Post by **Seankevinorourke** » 10 Aug 2018, 17:00

I’m having the new maf retested Monday as it was installed by my mechanic after running full diagnostics . If it’s bad I’ll have him put in a Bosch. The filter is Bosch, plugs are 3prong Volvo. Cables are original. No smoke. I’ll try a cap and rotor. He said fuel pressure was good.