Power delivery issues and poor fuel economy

[Chris GTO TT]

My Car has been doing this for about as long as I've owned it. The low RPM power delivery seems very poor and not linear to me. Between 2000 and 2750 rpm the car seems to load up and be very sluggish to respond to throttle inputs. I also seem to get a bit of a vibration in that RPM range as i accelerate through them. I've logged that rpm range and nothing seems out of the ordinary, no knock, timing looks fine (can't recall the numbers) etc.

Also along with this issue I've never had very good fuel mileage. The best I've ever recorded is 22mpg with it being mostly highway. Normally I average about 18-19mpg.

I've checked the timing belt and all timing marks line up.

[DocWalt]

Have you verified that the O2 sensors are behaving properly? Just recently, my rear O2 stopped doing full cycles and the ECU leaned the trims out nearly all the way and made the car drive exactly like you're saying. Sluggish in that range, and fine everywhere else.

[Chris GTO TT]

I suppose it couldn't hurt to replace both O2 sensors, but iirc they do cycle properly

Who sells plug and play O2's?

[DocWalt]

FWIW, mine looked like they cycled properly, but didn't. Hard to explain, lol.

Advance Auto does, if you want locally. I just recently bought some from Rock Auto, super cheap.

[TooFast4Radar]

I always go to OEM on those sensors. They might cost a little more, but you know they are right and they're plug-n-play.

[DocWalt]

Rock Auto sells the OEM sensors, which is why I went with them the second time around. Advance sells Bosch. Both plug and play.

[Chris GTO TT]

Isnt OE bosch anyways?

[DocWalt]

Pretty sure it's Denso.

[Chris GTO TT]

yeah found the denso ones on amazon for 96.46 gunna order em.

[DocWalt]

I just paid under $50 for one from rock auto...

[Chris GTO TT]

DENSO Part # 2344887 $118.99 on RockAuto, $96.46 on Amazon
DENSO Part # 2344886 $126.79 on RockAuto, $97.97 on Amazon

[DocWalt]

Weird. Does the 1G use different sensors? My front O2 would have been something like $35 from Rock Auto.

[Chris GTO TT]

From what i was seeing only the 91 and 92 cars used those part numbers so it must be.

[DocWalt]

Didn't know that.

[Chris GTO TT]

Yeah it was news to me too

[DocWalt]

Weird, I can't "thank" you here.

[B-Man]

22mpg really isn't that bad. It's about what I got going to UMG which was a whole tank of highway driving. What pressure/turbos are you running?

NG in TN I got 13mpg with city/racing :lol:

[Chris GTO TT]

Only mods on the car are: intake, downpipe, and boost controller set to 13-15psi depending on my mood.

[Drweldin]

Have you inspected your ECU board? That would be the first place I'd look...

[Chris GTO TT]

Yes its clean and new capacitors soldered in about a year ago.

[RealMcCoy]

I had one with similar symptoms that turned out to be low voltage to the fuel pump on the low load (resisted) setting. It would lean out just before the relay switched, then come back alive after it switched.

I never bothered to figure out why, it was getting a hotwire anyway, which fixed the problem completely...

[MaxClass]

Just replaced both front and rear on my Fiances '93 Stealth RT Twin last weekend. It had failed smog on Saturday, replaced them Sunday morning and took it in again and it passed.

Bought both front and rear at Auto Zone for about $68.00 each manufactured by Bosch. By the way. Auto Zone's computer shows that all generations of Stealths have four sensors but you only need two on years 91 through 93 for certain.

The front one is Bosch part number 13801 and the rear one I used [because they did not have the factory wired one] is a universal one part # 15733 that has what they call a SmartLink Kit that adapts the wires to you OEM plug end. Took a little figuring out on the wires but was otherwise quite simple.

Bottom line: It worked perfectly.

MaxHints:

Auto Zone rents [$25.00 refunded when you return them] a set of crows feet adapters to fit over the wires to remove the O2 sensors. Replaced the front one first by only removing the section of flex IC pipe and the front exhaust heat shield [3 bolts]. Slipped the 7/8" short crows foot on the O2 sensor with the extension flange facing downward. Could not get anything on it to turn it so I held it in place with a long screwdriver and set my breaker bar on top of the flange so I could drive it downward to loosen it by hitting the other end of the breaker bar with a large rubber mallet. After about the third hit it came loose. A couple of readjustments of the crow foot and I was able to remove it by hand. Make sure you use some type of anti-sieze on the threads [I used my ARP Ultra Torque, great stuff]. Could not find a way to tighten it once I got it screwed in by hand. My Fiance looked at it and said it looks like you can get to it from underneath so I jacked up the front, put a jack stand under it and crawled under and sure enough you can reach it fine with a 7/8" box open end. Tightened it up easily. Jeff Lucius' site shows removing tons of stuff to get to it but I can testify that you only need to do the above to do it.

Rear one is a cinch. Just remove the rear turbo tube, use the long crows foot adapter and a breaker bar and it comes out easily and goes back in just a easily.

Hope this is of some help to someone.

P.S. If you don' have any of the "ARP Ultra Torque Assembly Lubricant" you should get some. I bought the 10 oz. bottle and use it on every nut and bolt now. Talk about smooth and has anti-seize capabilities. Those folks know what they're doing. Trust them.

[Chris GTO TT]

Thought i'D up date this thread too. As of right now it seems that the new O2 sensors have fixed this problem but i've only driven my VR-4 about 15 mi since getting the new sensors in.

[DocWalt]

Sounds good. You have a logger, I assume. How do the trims look?

[CoopKill]

So, I noticed on my logger a couple months back my rear o2 was not cycling properly (not a wave sign). I replaced it and did not bother to check it until last week.

It looks the same as before. The front has a nice square wave signal, but the rear looks flat jagged and crappy.

Any thoughts?

[DocWalt]

You shouldn't have a square wave signal on the front one. It should be a normal looking sine wave. Is the rear generally following a sine wave, with some little jaggies, or is it horrible? Are you only logging O2s to get better logging resolution?

[CoopKill]

The front may not be totally sqare at the peaks, but the look consistant at idol.

The rear looks mostly flat with random jaggedy crap.

I am driving it tomorrow, I will hook it back up and refresh my memory.



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[DocWalt]

OK, that sounds more normal for the front. The rear sounds... bad, lol. Post up an update :)

[Chris GTO TT]

I still havent done a full log yet on my car I will up date when i do

[CoopKill]

I logged a few minutes ago and the front o2 looks very constant and the rear is not as bad as I remembered.

Rear at idol is pulsing about twice as fast as front and has a bit of irregularity to it.

When I hit the throttle out of idol rear gets a nice sign, but is about 1.5 more freaquent.



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Tapatalk Bitches! :transform: