Stumbles on acceleration

[sl92q45]

O.k i've got a 92 q45 with 123xxx, i've replaced knock sensors, Cas, and currently have no codes 55. The car idles a little high in p about 800ish revs up no problem in P but in drive under load their is no power and car really struggles. Injectors are all good as well as fuel pump. Is this vacuum related ?

[goody90q45]

O.k i've got a 92 q45 with 123xxx, i've replaced knock sensors, Cas, and currently have no codes 55......

If you're reading the codes properly and the CEL is not coming on then I suspect there is something wrong with the fuel delivery system. If the CEL is coming on you may be reading the codes wrong since the instructions in the manual can be confusing. Have you checked fuel pressure at idle (34psi) and full throttle (40psi)? Any humming from the fuel pump? Have you tried bypassing the FPCU? Let us know.

Where are you? Someone may live close with a laptop consult.

Welcome to NICO!!

[sl92q45]

I live in Clearwater fl, i don't have a cel light and my fuel pressure is 34 at idle and 40 when you hit the TB. Car starts on first crank every time, pump humms when priming sys but not really when at idle, tank is also on empty as well, i'm thinking bad gas and tring BG44 or fuel rail flush. Anything between transmission and ecu that could cause this. Oh yeah and shes white ext. with beige int. walnut dash and on 18'' Come on Nico help a newbie.

[goody90q45]

With no CEL I'm still thinking fuel system so there's one more quick test for you- bypassing the FPCU and driving under a load vs. measuring pressure at idle. Reach in through the trunk and unplug the FPCU connector (in the background in the pic). Any burn marks on the connector pins? Jumper from the pin shown in the pic to chassis ground. The FPCU ramps the fuel pressure up and down and may have a bad circuit. Take the Q out for a drive and let us know if it helps.

You did change the fuel filter? Ohm test the injectors? One bad injector may not light the CEL.

[elwesso]

I agree with goody.. check out the fuel pump like he mentioned and report back.. if the fuel pump has not been replaced that you know of, you will need to replace it most likely.. Thats one of the few things on the Q that you're guaranteed to replace sometime.

[sl92q45]

Ok i have a new fuel filter and all my injectors are within spec. I tried the fpcu bypass and blew my fuel pump fuse,tried this twice and every time it blew so i could not start to test drive. What ground on the body did u use, i used the strut bolt . Every 3 or 4 starts it tends to slowly increase idle to about 1500-1800 rpm or slowly backs down then up kind of searching and other times it sits right around 800rpm any ideas?

[goody90q45]

I tried the fpcu bypass and blew my fuel pump fuse,tried this twice and every time it blew so i could not start to test drive. What ground on the body did u use, i used the strut bolt ......

There's no reason why bypassing the FPCU should blow fuses but the strut bolt may not have been the best choice of grounds either. Use the frame in front of the fuel tank for a solid ground. You should have unplugged the connector from the FPCU shown in the background in the picture, it's by itself on the passenger side of the rear parcel deck, and from the connector that was unplugged fab a jumper wire from the pin shown to the frame in front of the fuel tank. Ensure solid connections on both ends, i.e alligator clips.

.....Every 3 or 4 starts it tends to slowly increase idle to about 1500-1800 rpm or slowly backs down then up kind of searching and other times it sits right around 800rpm any ideas?

Is it dropping down to 100rpm also during the search? Sounds like a Mass Air Flow (MAF) sensor problem but it doesn't explain why the CEL is not on. For kicks, pull the MAF connector and clean off any corrosion, tighten the pins to look like the middle one in the pic, and lube them with dielectric grease. Clean and lube the MAF pins as well. If your seeing corrosion at this connection it will be on other similar connectors (CAS, TPS, EGR solenoids). They'll need cleaning.

This still doesn't explain no CEL. Do the FPCU bypass first to rule that out. It should only take a few minutes.

[sl92q45]

I did the bypass and now i can hear the fuel pump running. The stumble is still there and the engine makes a chug, ping, sounds like knock and doesn't rev up quickly at all. I think i'm running rich cause the exhaust smells like gas. Cleaned the maf whith electrical cleaner already. What is the factory set of the idle air valve. Thanks for your help guys, so close to driving it i can smell it. Whats the best program for the consult and where can i get one, found the consult 2 on ebay for 15 bucks but their program doesn't allow factory overides.

[BCC93QT]

Well i see no one has informed you about the timing chain guides..........unless i am blind. check the topics on the top of the page before u even fill ur tank up again mang