2.5L ('98-'01) 2.5 rough idle while warming up

[Bunger317]

I recently picked up a 2000 2.5 manual ranger. Seemed to run great on the test drive. Motor has 197k on it and has reciepts for a rebuild at 176k. First day I drove it to work I let it warm up in the driveway while I made my lunch ran fine to work. Leaving work it didn't have time to warm up and once I got to the second stoplight and came to a stop it started idling horribly shaking vibration almost stalling. Had to crack the throttle to keep it running. Once it got to full operating temp it smoothed out and was fine. Does it everything single time it's started from a cold dead sleep. I've done plugs wire fuel filter pcv valve. Test egr by sucking on it. Iac looks new. Cleaned it anyways. Cleaned maf and map sensors. Can't seem to find a fix for this. I've never owned one before so have nothing to base it off of but it seems pretty under powered. Checked compression and got 150 on all 4 cylinders on a cold motor. Could it be a timing belt issue? It looks original. Possible leaking valves? Never had an issue like this and I'm baffled.

Also, mileage appears to be complete garbage. Fromwhat I've calculated im
Getting 14-17mpg.

 

[Bunger317]

Once warm it isles pretty good. Some days the idle will ramp up and down slightly or surge but usually will idle smooth once warm. Also no CEL or stored codes. I have noticed a exhaust leak type noise under load between 1500-3k rpms. Haven't been able to locate an exhaust leak though. Also put a vacuum gauge on the port where the fuel pressure regulator line connects and got 18" of vacuum.

 

[Bunger317]

Also, tested for vacuum leaks with propane and brake cleaner, can't find any leaks. Sometimes unplugging the aic lowers the idle sometimes it doesn't. I have a Bluetooth obd2 and the fuel trims go nuts when it idles rough like it's trying to compensate. I read the ecu is in a open loop while warming up. Wondering if it's something with switching from open to closed loop program in the ecu when it comes up to temp?

 

[Bunger317]

Here are some screenshots during a rough idle warmup. Also I want to try to WoT injector leak start test but I only 89% throttle position at wot. Does that sounds right?

 

[Bunger317]

Did the WOT start test for the injectors. It sputtered and tried to start. So I'm assuming the injectors may be leaking? Anyone?

also filled her up today. 16.5mpg was my average. Driving pretty conservatively as well.I get the same mileage in my 5.3 gmc. Somethin ain't right

 

[Bunger317]

Damn, tough crowd

 

[Bunger317]

No one has any insight at all?

 

[Bunger317]

This forum is a joke

 

[scotts90ranger]

I'd have posted some ideas if I had anything that sounded good... Something isn't reading right, I'm not the most up on MAF systems but they're not that complicated, the fuel table will have engine speed and MAF axes likely, same with spark table, the main modifiers are going to be for coolant temp and slightly less for air temp. So either the MAF signal isn't getting to the computer reliably, the computer has an issue, or there's an issue with the crank or cam sensors, or the fuel pressure or fuel injectors aren't behaving properly unless it's interpreting the O2 sensor wrong but since you said it ran better once it was fully warmed up which makes me think the engine wasn't getting the right amount of fuel and the O2 corrected for it... There's a lot of variables... I think the cheap OBD II deals that use the Torque app will show the MAF reading and I know they show the long and short term fuel trim values, both of those together will tell you some things, either the MAF is reading high or low and the O2 will be high or low which will give good info...

We're all volunteering our ideas and time, I've surfed the web enough to know this forum isn't a joke, most automotive forums have a bunch of speculation from people that own engines, know wings make the car faster and stickers add power... I understand the frustration though...

 

[Bunger317]

Replaced both o2 sensors with Bosch units after getting a "heated o2 sensor slow response" code. No improvement. Since I last posted I got a quick cylinder 1 misfire. When it has its cold roughly idle episode I know the STFT shoots up to +30-40%. Still getting crap mileage. Struggle to get 220miles to a 16 gallon full tank. I have determined that cylinder 1 spark is intermittent on 1 coil. But with 2x coils I can't see that making this drastic of a issue. Leaning towards injectors still. Also still have a pretty loud exhaust leak type noise only under load.

 

[Bunger317]

MAF and coolant/intake temps stay really stable and don't have any spike or anything

 

[scotts90ranger]

I just changed my injectors last weekend on my '97, was having hard start sometimes from some leaky injectors and apparently some restricted injectors, it shook sometimes and hesitated... decided on rebuilt injectors which I found on Amazon for $120 for a set, took an hour and a half and runs better, didn't change my mileage though yet but bad time of year to check mileage...

 

[Bunger317]

I just changed my injectors last weekend on my '97, was having hard start sometimes from some leaky injectors and apparently some restricted injectors, it shook sometimes and hesitated... decided on rebuilt injectors which I found on Amazon for $120 for a set, took an hour and a half and runs better, didn't change my mileage though yet but bad time of year to check mileage...

Thanks for the reply. Did it help the other rough running issues you had? Would you mind posting the link to the ones you got?

 

[scotts90ranger]

The ones I got won't work on a 2.5L, they'd fit but in '98 with the returnless I think they went to higher fuel pressure and different injectors, with that I got THESE, but I think you need THESE but I'm not seeing some rebuilt ones, maybe on ebay or rock auto...

 

[scotts90ranger]

I forgot some of your questions, it's too early to tell on some of the runability on it, the stumble wasn't very consistent or common, mainly on a hot restart and if I had to guess it was the transition from open to closed loop fuel control while under light acceleration... On the startup where it would flood out, it seems to have helped that as it didn't catch (cranked a split second too short) when I started it after work but then started right up next try... the fuel mileage seems the same so they weren't that bad though...