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ST-185 Sluggish before turbo spools

PostPosted: Tue Oct 03, 2017 12:02 pm
by bullet781
Probably a stupid question, but here it goes:

93 'trac, essentially bone stock with 155k miles. Newer plugs, wires, cap (18 months ago), new cat (2 weeks ago), all major services done/updated/taken care of by and large. Great car...runs really, really well.

Except for the last few weeks - whether the engine is cold or hot, engine feels like it bogs down significantly/loses power UNTIL the turbo spools and then it responds great - like always. I've done the usual checks and tests (per all the discussion I've seen and searched through in other posts in the forums) but I am stumped.

Could it be the 02 sensor? They've probably seen better days. Maybe the EGR valve? Of late, she smells like she's running a little rich.

Open to thoughts or things I should investigate and try - hopefully it's nothing major. This think has gotten a significant overhaul this year - can't afford much more!

Re: ST-185 Sluggish before turbo spools

PostPosted: Tue Oct 03, 2017 3:19 pm
by underscore
Sounds like it's running rich, maybe the O2 sensor or a pre-O2 exhaust leak. Try unplugging the sensor and see if it gets any worse?

Re: ST-185 Sluggish before turbo spools

PostPosted: Wed Oct 04, 2017 12:11 am
by bullet781
Unplugged the O2 sensor and it’s a bit worse (driven about 25 miles disconnected). I can always replace my to see if that helps matters. Only noticed it after the cat was replaced two weeks ago - but we’ve double and triple checked and no leaks or issues with the cat thus far.

Re: ST-185 Sluggish before turbo spools

PostPosted: Wed Oct 04, 2017 7:05 pm
by lalojamesliz1
Take a look at the spark plugs and if they are black on the ends your running rich and that can point at what underscore suggests.

Have you tried a compression test or leak down test?
Also , verify the engine timing

Re: ST-185 Sluggish before turbo spools

PostPosted: Thu Oct 05, 2017 3:32 pm
by MADDTRD
Have you checked the compression of each cylinder?

Re: ST-185 Sluggish before turbo spools

PostPosted: Mon Oct 30, 2017 5:06 pm
by bullet781
So as an update, we've checked all things recommended and mentioned so far in this post (thank you to all the replies) with no change in bucking at low RPM's and it's running really rich. Plugs, wires, distributor, checked/adjusted timing, etc. Disconnect the O2 sensor and it's still the same. No leaks...no smoke...once it gets going, it's fine. It's getting it going that's the problem...anything below 25 mph and it feels like it will stall. No codes or CEL. At wits end and ready to give this car up at this point. Could it be a bad ECU? Bad cold start injector (which are near impossible to find)? I see a few ECU's floating out there on eBay but can't make sense of whether one of them will be a good swap or if I should send mine in somewhere for a repair/rebuild? Open to any other suggestions, but I'm out of good ideas (and money)!

Re: ST-185 Sluggish before turbo spools

PostPosted: Mon Oct 30, 2017 7:22 pm
by lalojamesliz1
bullet781 wrote:So as an update, we've checked all things recommended and mentioned so far in this post (thank you to all the replies) with no change in bucking at low RPM's and it's running really rich. Plugs, wires, distributor, checked/adjusted timing, etc. Disconnect the O2 sensor and it's still the same. No leaks...no smoke...once it gets going, it's fine. It's getting it going that's the problem...anything below 25 mph and it feels like it will stall. No codes or CEL. At wits end and ready to give this car up at this point. Could it be a bad ECU? Bad cold start injector (which are near impossible to find)? I see a few ECU's floating out there on eBay but can't make sense of whether one of them will be a good swap or if I should send mine in somewhere for a repair/rebuild? Open to any other suggestions, but I'm out of good ideas (and money)!


Have you opened your ecu to make sure you don't have any leaking capacitors or have anything burned up?
I personally don't think the cold start injector is even needed because it started fine for me when I first got my all-trac back and it had gen2 electronics on my gen3 engine (No Cold start injector). I'd try unplugging it from the fuel line and plugging that hole. I don't remember the bolt size unfortunately

Re: ST-185 Sluggish before turbo spools

PostPosted: Tue Oct 31, 2017 1:21 am
by Celi-GT4
Did you double check the timing, whats it running?? How about the t belt are the cam pullys looking lined up at
TDC? Any hanging valves?

Re: ST-185 Sluggish before turbo spools

PostPosted: Tue Oct 31, 2017 2:54 am
by FC Zach
I've had the exact symptoms before. . . This was years ago but I believe my AFM was the issue.

Re: ST-185 Sluggish before turbo spools

PostPosted: Tue Oct 31, 2017 2:57 am
by FC Zach
I also replaced the O2 sensor around the same time, that could have been the fix. . . I don't remember for certain.

Re: ST-185 Sluggish before turbo spools

PostPosted: Tue Oct 31, 2017 3:17 am
by lalojamesliz1
The process of elimination.... sucks man.
Have a wideband? That would help I'm sure but at a price tags of like $150+

Re: ST-185 Sluggish before turbo spools

PostPosted: Tue Oct 31, 2017 3:57 am
by underscore
Isn't there a test procedure for the MAF? I'd try that. A sticking cold start injector could also cause the car to run rich.

Re: ST-185 Sluggish before turbo spools

PostPosted: Tue Oct 31, 2017 4:33 am
by FC Zach
underscore wrote:Isn't there a test procedure for the MAF?


You're helping me remember. . . There is a test procedure, an ohm meter will be needed. I recall testing mine now, I'll share the page from the manual if OP doesn't have one. . let me know.

Re: ST-185 Sluggish before turbo spools

PostPosted: Wed Nov 01, 2017 1:43 am
by bullet781
I don't have the test procedure, so if someone would be willing to post it/share it, that would be fantastic.

Pulled the new o2 sensor - it's pretty black. when it's not connected, there's no difference with the performance of the car, which is why I was wondering if there's something to do with the ECU. Ran fine for years...and then, one day, it happened. Out of nowhere...

I've heard that the cold start injectors for these cars are interchangeable between other models - if that's the case, can anyone point me in a direction to what to look for?

I'll pull the ECU next to see if there's anything burned out. How interchangeable are these? I've seen a few come out on eBay from time to time, but wasn't sure how the numbers needed to line up? Or...am I better off having it reprogrammed?

Re: ST-185 Sluggish before turbo spools

PostPosted: Wed Nov 01, 2017 4:15 am
by FC Zach
bullet781 wrote:I don't have the test procedure, so if someone would be willing to post it/share it, that would be fantastic.

Will do, when I get off work in the morning I'll check the manual and share the procedure.

bullet781 wrote:Pulled the new o2 sensor - it's pretty black. when it's not connected, there's no difference with the performance of the car, which is why I was wondering if there's something to do with the ECU. Ran fine for years...and then, one day, it happened. Out of nowhere...

I'd replace this regardless. . It's a tune-up part, wont hurt.

bullet781 wrote:I'll pull the ECU next to see if there's anything burned out. How interchangeable are these? I've seen a few come out on eBay from time to time, but wasn't sure how the numbers needed to line up? Or...am I better off having it reprogrammed?

They are model/year specific so you'll need the proper part.