Trying to iron out a few kinks after acquiring this beauty.

1986 740 wagon - non turbo
190 000km
Automatic

Ive been keeping track of my gas mileage and a full tank is getting me approx 350km! Give or take

From what i read i should be getting close to 525 or so of mixed driving.

So far
I have cleaned out the flame trap
The IAC
(Both were not bad at all to begin with)

Previous owner claims he has changed the wires, plugs, rotor , cap)

My idle has been a bit weird as of today
With it in park i rev her up to 3000 and then it with drop to 1100 and sometimes stay there.. Other times it will drop to the normal 800-900 after a few moments

On cold starts if i start her up and drive her off after a minute of warming up she seems like shes either getting too much gas or not enough and is at a loss of power for a 100feet. But only for the first pull after 100 feet on a cold start.

I bought a coolant temp sensor today
But i was thinking it might be the TPS..?
I will clean the throttle body tomorrow when the gasket gets to the parts store.
Maybe the knock sensor?


Any input would be appreciated!

Thanks

 

I'd change out the cts since you have it and if you are pulling the throttle body to clean it, then adjust the tps by turning clockwise then counter clockwise until you hear the click and then tighten the screws and see if that works. It could be the knock sensor, but I don't know that the symptoms would go away after it warms up- but I guess it's possible. Any detonation when you put your foot in it?. So yeah, do what you are going to do.

What did you clean the iac with?
What brand of ignition components did the PO put on the car?

 

Your gas mileage readings are far from scientific.
You should be getting 20-25 mpg, you have 15 gallon tank, more or less. This is 300-375 miles, 500+kms. So, yeah, you are right, mileage is bad.

Start with the basics: a good tune up, (make sure the PO parts are of good quality), assure good tire pressure 32+PSI, etc.
Any black smoke on acceleration?

 

I swapped the COolant sensor but that did not fix the problem (at least the old one looked like it was time to change )

I took off the throttle body and have it a rly good cleaning with the proper intake cleaner. Put it all back together and the fluctuating idle pretty much went away and i have regained quite a bit of power! Even my spouse pointed out from the passenger seat that it seemed like the car was driving lighter!

Now for a final test i need to fill the tank and see if this resolved the gas consumption. Fingers crossed!

 

Glad it's running better.

Did you replace the coolant sensor that has one wire or two?
----
Suggest running a bottle of lucas fuel injector cleaner. I have run it for many years and it does work for mileage and for smooth running.

Really suggest looking at the ignition components (plugs, wires, cap. rotor etc.) to see if they are the correct brand and type. Do you know which fuel injection/ ignition system is on your car? These cars can have really odd and poor running conditions due to substitute ignition parts; no kidding.

Utilizing these correct parts and doing a tune up, air filter, timing, etc is essential to establish a baseline so one can "go from there".

Between Ipd and FCP Euro and similar companies, the correct parts can be had for not much money.

Incidentally, FCP euro also sells the Volvo CD Rom service manual as well as the paper Chilton and Haynes manuals (for the 740, the CD Rom is the way to go) if you want to be more involved in learning about your car and to supplement what you can learn here.

https://www.fcpeuro.com/Volvo-parts/...4&m=207&page=1

 

Since the day i got her i have used lucas oil injector cleaner a few times.

I changed the temp sensor with harness going to it, the one with a single prong is just for the dash gauge.

I will be checking the ignition parts this weekend.

Thanks for the awesome replies guys !

 

After a day it still has good power but the idle still drops a bit and oea back to normal when im at a red light. It doesnt do it all the time. Could it still be the tps?

 

Looking at your thread, it reads that the idle instability began after cleaning the IAC. What did you clean it with?

 

The idle has been always high since i got it, i noticed it was very bad on gas too.
I cleaned the throttle body and i regained power and the idle lowered. Now the idle is dropping at red lights sometimes. Im wondering if its the tps.

I will hopefully find time to check spark plugs this weekend as well as plug wires, rotor and cap.

 

stick your favorite tube/pipe/hose in your ear and listen everywhere possible for vacuum leaks.


I diagnosed my bad timing belt tensioner bearing today using a pipe from a vacuum cleaner!

 

The throttle position sensor allows for voltage to power the Idle Air Control valve when the throttle closes. If the throttle does not fully close it will produce a higher idle and also the IAC will not run. The TPS should click as soon as there is any movement of the throttle, so see that it does click as soon as you move the throttle in the engine bay. If it does not, slightly loosen and adjust until it does.

For sure also check for vacuum leaks including on the large intake tube between the AMM (MAF) and the throttle body. They can sometimes wear a hole on the bottom side. Very important for helping establish a baseline.

 

high idle suggests lean condition. possibly. Again, check for airleaks.

LH2.2 also has an idle mixture screw, but just dont go tampering with it. There is a procedure involving a CO meter. That's all I know right now. lh2.4 ftw!

maybe clean maf with MAF cleaner. It can cause lean condition and idle issues.

 

I did not adjust it.. And the tps clicks pretty mich right when the fly opens... So weird how the idle was fixed and regained power after cleaning the theottle body. And a day later the idle is almost acting the same! Stays in high idle at times with it in neutral.. Like 1200-1300rpm and with it in drive at a red ligt the rpm keeps bouncing from 900 to 600..

 

check o2 sensor for boltage swinging between .1v-.9v once the sensor is hot.....


I am part of the 420 miles per tank club.

 

im very confused as this seems to really be linked to cleaning the throttle body and a day later its back with the same symptoms! so frustrating!


maybe this will help narrow it down..
when i give it gas in park is the rpm supposed to drop right to its original spot or is it supposed to stop for a second at around 1100 and then slowly go down to the right rpm?

 

You need to first make sure the throttle body parts are all adjusted PROPERLY and then you need to make sure the TPS is doing its job.

From my experience, especially on LH2.2 cars, previous hacks have almost always fiddled with all the throttle adjustments trying to fix unrelated problems. IE. my car is running rough, maybe i should crank open the idle speed screw...WRONG!

Look up how to dial in your throttle body, then adjust tps after.

This is for 2.4 throttle body adjustment, but i dont see why 2.2 is any different. If you actually read the document carefully and perform the tests, which nobody seems to do around here, it will walk you thru the basics of why your engine may be running ****ed up starting with the most common things like airleaks, bad grounds, fuel pressure issues.

http://www.volvowiringdiagrams.com/v...20Complete.pdf

It's too hard to understandm using your explanation, if you are even having issues with high idle. Ya, sometimes it takes a second for the rpms to drop back down from over 1k when the throttle is closed quickly. If you have other problems, it can also show up in your idle.

Have you even bothered listening for airleaks yet, or do you expect us to e-diagnose it over the internet?

 

For a guy who three weeks ago had thrown

"Not a dollar fired from the parts cannon! I lied...kinda....I did toss a crank sensor, ICU, and main pump at it with no luck, but they were sitting on my shelf. "

before asking people on this forum to e-diagnose your BAD PLUG WIRES while utilizing a weak three year old Walmart battery and having re-routed your oil- degraded wiring over the top of your engine and being fine with having to bump- start your car just how do you get off talking to other forum members this way? or is that the point? Condescending. LOOK IT UP!

 

if you goose it in park, it should rev up and nearly immediately drop back down to idle, no delay. to me, any delay suggests your throttle is still sticky.

the throttle position idle switch is an input to the ECU, when the ECU sees that is closed, then it monitors the RPM and uses the IAC to stabilize it at ~700 rpm, by sending it pulses to open it and allow more air in. as soon as that switch opens by cracking open the throttle, the ECU stops the idle air control.

 

That could have caused your problem. Years ago I cleaned out my IAC then had idle problems later. Read up on it, and found information suggesting that cleaner could damage the IAC if you get it down into the guts of it. The information suggested you should clean it hanging it with the openings downward.

That was about 15 years ago, and I have never cleaned an IAC since! I have never had to. I have yet to even see one gunked up, but not saying its impossible.

 

indeed, whenever cleaning something that has an electrical component like a MAF or IAC, hold it so the electrical bit is on the high side, and the tube is at a 45 degree angle, so the solvent doesn't wash crud into the electrical part. the IAC has a solenoid that lifts a 'shutter gate', this has to move quickly and freely and snap back into position.