I have an 1994 850Turbo wagon. For about a year, the check engine light has come on reqularly with the 231 code (Long term fuel trim at limits at partial throttle, I check it and turn it off before a long drive. The other day on a road trip from CO to Kansas and cruising at 70mph, my car kind of hiccuped and suddenly the gas mileage dropped from 28-30mpg to 15-17mpg. I stopped for the night and the next morning for the first 20 min or so of my trip the mileage was good again...back up to 28-30 then the hiccup and mpg plummet again! The check engine light did not come back on during this whole thing. I took it in to a shop for European cars (never been there before) and they checked the codes...pulled 2 codes, then drove it around and pulled 24 codes!!! all that I have never seen before. They started checking stuff...air mass meter, coolant temp sensor, ignition system, turbo system, ECM power supply, fuel pressure and everything checked out as fine. I cant afford for them to continue diagnosing it....they said it would take 5-6 hours to check all the wires. Anyone ever had this happen before?? Could it be spark plug related? I just changed them a month ago but learned that they were not correctly gapped after changing them, could this cause such a huge issue? Could my whole engine be bad?
Some codes...
Tank Pressure Sensor, Rear H02S signal, Long term Idle air trim, Injector1, 3,5, ECM Temp Sensor, Fault in ECM, VSS signal, IAC Valve Closing signal, MAF sensor, TC Control Valve, Cyl 3,4 Misfire, Powerstage group B, C, E; MIL Request TCM Link Failure, Air Pump Sensor,

All these codes just appeared after the mechanics drove it..none that I have ever gotten before when checking the codes. No trouble ever starting it. I drove it from the shop and it seemed to be running great again after sitting for 12 hours...no codes yet, but I bet 30 min on the hwy would make the gas plummet again. Has anyone ever seen their gas plummet like this?? Please help!!

 

yes though what happend to mine was the fuel line in the tank was barely one the sending line so itd run but not hold pressure causing me to get horrible gas mileage.

 

I don’t think your engine is bad. Plugs with an incorrect gap wouldn’t cause a hiccup (but make sure you get them gapped right!). If there was a hiccup, maybe the catalytic converter broke apart and there was a partial clog?

If you can read and reset the codes (sounds like you can), reset ‘em and take a drive. As soon as the hiccup appears or the CEL goes on (remember; not every error code will trip the CEL), take another reading and pass along the codes. If the 24 codes appear all at once, I’m going the guess that there may be a vacuum hose lose somewhere.

 

I am betting on vacuum hose also. I will know for sure once I see the codes so let us know them as soon as you get a chance.

 

Thanks for your replies! After about 48 hours of minimal driving (to and from the mechanic) I finally replaced the spark plugs with Volvo 850 specific plugs, drove the car on the hwy for 30 min at 65mph and everything seemed fine, hit the road for a 6 hour trip cruising at 65mph and was getting 30mpg.

After 3 hours of driving I bumped my speed up to 70mph since the speed limit changed and within 15 min there was the hiccup (kinda feels like a brief acceleration and then a release). It happened a few times and the gas plummeted. The car seemed to be shaking a lot more the rest of the drive..or more like a strong vibration with a few more hiccups along the way, but those hiccups did not seem to make a difference. I thought I was home free with the spark plug change, but I guess not. I did stop to read the codes about 5 min after it happened and there was still just the one code 231 (long term fuel trim at limits at partial throttle) I am going to take it in to the family mechanic and have him check out the vacuum connections.
Is there a way that I can check this myself?
If just keeping it at 65 will help then I can do that. Is there a reason 70mph would make this happen?

 

I'm not familiar with the 1994 850 Turbo - do you have an automatic or manual transmission? What about overdrive?

If you were fine when traveling at 65 mph for hours, and then had the problem when you kicked it up to 70, it would seem that there's something (like overdrive) that kicks in because of the speed difference.

Where you using cruise control during this last trip, or at any time when you experienced the problems?

You can check vacuum hoses visually, as well as give them a feel to see if they're brittle or damaged in any way. You can probably feel around for cracks on them, too. You can search the board for a diagram of where they run - it looks more like an electrical schematic than photos, but they help identify where the hoses connect.

 

I have an automatic and I was definitely using cruise control...the whole time.

I know I have a number of hoses that are brittle and look to be cracking so it could be many leaks.

 

Replace the vacuum lines. It's no coincidence with the cruise control use as it's vacuum activated/regulated.

 

Is there a particular vacuum line I/my mechanic should be looking for that is bad?? are you suggesting, replace all of them?

 

Go with all of the cruise hoses. The cruise control module is mounted under the battery tray and I think there's three hoses hanging off of it.

 

You can replace all the vac hoses but you would just be guessing at the problem. DTC 231 (see below) just means the fuel trim (adjustment) is at its limit; doesn't tell you which limit; i.e. could be rich or lean. You will need a scan tool to learn more. If you have a fuel pressure gauge i would start by cking that. And/or take it to your tech. Are you getting any blue smoke out the tail pipe?


Below from 850 turbo manual:
=============================================
Code 2-3-1 (Long Term Fuel Trim Partial Load) Or
Code 2-3-2 (Long Term Fuel Trim Idling)
1) Check for other codes. If Code 3-1-5 is stored, perform
testing on that code first. If Code 3-1-5 is not stored, go to next
step.
2) Check status message on Volvo Scan Tool (998-8686). If
status message reads LOWER LIMIT, go to step 8). If status message
reads UPPER LIMIT, go to next step.
3) Turn ignition on. Connect voltmeter between MAF sensor
connector terminals No. 2 and 4. If voltmeter reads .1-.2 volt, go to
next step. If voltmeter does not read .1-.2 volt, test using new MAF
sensor.
4) Check for air leakage in intake system. Repair as
necessary. If air leakage in intake system is not present, go to next
step.
5) Check for air leakage in exhaust system. If there is no
air leakage, go to next step. If there is air leakage, repair as
necessary.
6) Check fuel and residual pressure. If fuel and residual
pressure are okay, go to next step. If fuel and residual pressure are
not okay, repair as necessary.
================================================== ==
There's more but it references break-out-box equip, etc...

 

Havent noticed any blue smoke out the tail pipe. Mech checked the cruise control hoses and other vacuum lines they seemed good. Of course they could not recreate the problem when they took it out at 70 on cruise. They wont have time to continue with it today, fri, so I am gonna pick it up for the weekend and go ahead and drive it around.
Where can I get a volvo scan tool? Obviously I am a beginner at all this, but I love my volvo...have a ton of money invested in it already, so I want to figure this out.

 

Your '94 should have an ODBII connector, which is under the coin tray just in front of the shifter - just grab the back end and pop it up. You can pickup any ODBII scanner at any auto parts store. There's a some basic models (that will display codes & let you clear them) that go for 40 or 50 bucks and then there's some units with more bells & whistles that go for 100 bucks - or more. I think if you're looking for a true Volvo diag system, you're looking at a couple of hundred, if not a grand.

If you don't have an ODBII, then you can review this page:
http://www.troublecodes.net/Volvo/

 

I have been checking the codes and clearing them under the hood...the second way you suggested. Will the ODBII reader give me different codes? The mechs said they checked the fuel pressure and it was fine.

 

I would not be surprised if you have a fuel delivery problem like a fuel pump going out or a fuel regulator going bad or even a relay. I almost ran my R out of gas once and it hicuped while sitting in front of my friends house (idleing) and I got a CEL. When I pulled the codes I had so many that I just hit the clear codes button. I figured it was because the car loss fuel flow for a couple of seconds.

The sad part about your problem is that it's intermittant. You can pray that the problem just fails and be done with it (easy to fix a part that has totally failed instead of one that works 95% of the time) .

 

It has taken me a while to get some stuff done, but I took it to a tech and he did a smoke test, which revealed no vacuum leaks, so I changed the distributor cap (which was in fact the original with 155k).

It also appears I have no Turbo boost, which I never paid attention to before, because the needle (since I have owned the car) has never gone past the halfway point, but they checked for a bad turbo and found nothing wrong, so then they took a look at the cat converter and determined the the air on the exhaust end is cooler than the other end, which led him to believe that the cat might be melted, although it sounded fine to the hit.

Well, I broke down and got a new cat...$325 took it for a drive, didnt get any codes back, but the car was still shaking above 60. Turns out my cat was worn and partially melted but not in absolute need of replacement...go figure.

So then I replaced the plug wires (also original) last night (should have done this first before the cat, but oh well) and took it for a 70mph test drive and after 10 miles the CEL went on! Hallelujah! I got completely new codes! 522 and 153...everything pointing to the front and rear O2 sensor! Could this be my whole issue? should I replace the front first and then see if the rear really needs replacing too? cause doesnt the front send the signals to the bad one? Wouldnt this be causing my fuel to run lean? Which would explain my my former 231 long term fuel trim code with no vacuum leaks but bad rotor and wires.

Good news is that my rotor and wires needed to be replaced anyway so maybe replacing those made it easier for the computer to find the real problem. That however still doesnt explain my turbo boost problem...or does it? would an O2 sensor affect the turbo boost?

 

you shouldnt get good mileage one minute and then horrible the next with a failing O2, I would check your Turbo-Intercooler-Throttle body piping. a leak there would reek havoc on your A/F. I would check that first specially since your not getting any boost

 

I am a bit confused; your tech noticed you have no boost from turbo and determines you need to new cat to fix it? Sounds like it didn't....

You need to find a good indy volvo tech asap. BTW: the DTC codes 522 and 153 both point to the rear O2 sensor; double ck the connection and reset the codes before you go buy a new one.

 

1994 156,000 miles on it.

Sorry...the no turbo boost issue is simply another problem to fix. This was discovered in reviewing the car for leaks and such to try to determine the 231 code from earlier. I should probably start a new thread on the no boost problem that seems unexplainable.

Regarding the initial loss of mileage and constant shaking above 60mph and hiccuping....I cleared the codes, and did a hard restart yesterday, drove around and got just the 522 code which is Front 02 sensor heating faulty. gdog, are you suggesting the 522 is a code that results from a bad rear sensor??

Today I am putting on a new front 02 sensor, so I am hoping that it will fix my shaking problem, sudden drop in mileage at 70 and maybe the womp-womping sound I get when i accelerate.

91 shelby,I have been trying to figure out if I have a leak in the turbo intercooler piping. where should I be looking? I feel like I must be looking at the wrong thing. In looking up turbo issues on the forum many people have mentioned the intercooler hosing as being the issue when they have a very similar problem. I have revved the engine and squeezed the piping for pressure and it seems to hold pressure yet the wastegate is not opening (however the wastegate works, I have done a pressure test into the CBV and the rod moves to open the wastegate so somewhere I am loosing pressure. Could I have a bad boost control solenoid? I replaced the two rotting hoses going to and from it, but there was no change.

 

The intercooler has a total of 5 hoses - FCP has a picture of them (colored in red) here:
http://www.fcpgroton.com/product-exe...ategory_id/215

(there's a short hose on the right-side of the image that isn't colored but it is one of the hoses to replace.)

If those hoses are factory originals, then you'll probably want to change them all. That "the womp-womping sound" may be from a collapsed hose.